diff --git a/.oxlintrc.json b/.oxlintrc.json
index 66b09d7a2..820df7802 100644
--- a/.oxlintrc.json
+++ b/.oxlintrc.json
@@ -10,7 +10,7 @@
     "public/sdkjs/**",
     "public/web-apps/**",
     "public/fonts/**",
-    "public/libs/**",
+    "public/libs/sheetjs/xlsx.full.min.js",
     "public/ranui-iife/**",
     "public/ran-iife/**",
     "public/help/**",
diff --git a/CHANGELOG.md b/CHANGELOG.md
index dabf6ab74..4b7a1cd13 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,14 @@ notes. Entries describe what users experience, not internal refactors.
 
 ### Fixed
 
+- Exporting a PDF or another format keeps unsaved changes in the editable original visible until the original is saved.
+- Failed file opens restore usable file controls, including keyboard access.
+- Document history search keeps focus and ignores outdated results while typing.
+- Chat history conflicts offer an explicit way to keep local copies and restore saved conversations.
+- Dictation reaching its time limit finishes normally and preserves the final recognized words.
+- Spreadsheet conversions run in a background worker where supported, keeping the page responsive and canceling superseded opens.
+- Saving long chat histories avoids repeatedly processing unchanged conversations.
+
 - The language menu no longer flashes open and stretches the page header while
   the page is still loading.
 - Select lists and the dictation privacy note open above the AI assistant panel
diff --git a/docs/explorations/2026-10-26-reliability-and-responsiveness.md b/docs/explorations/2026-10-26-reliability-and-responsiveness.md
new file mode 100644
index 000000000..87004348b
--- /dev/null
+++ b/docs/explorations/2026-10-26-reliability-and-responsiveness.md
@@ -0,0 +1,85 @@
+# Reliability and responsiveness acceptance
+
+Base: `e06953cf25bb1d1849ba9af6c959d8b805388226`.
+
+## Changes
+
+- Other-format exports keep the editable source dirty and leave its SDK save point unchanged. A subsequent ordinary save still clears it.
+- Failed opens restore visible, focusable controls; visibility timers cannot race, and pages with a landing hero retain their distinct layout.
+- Document history retains its toolbar/input, rejects stale async results, and throttles expiry cleanup while forcing a sweep on BFCache restoration.
+- Explicit conflict recovery preserves all locally touched conversations as separate in-memory copies when they differ from saved originals. Saving remains off until the user opts in again. A later save still checks the loaded database revision. Old controller history handles cannot write into restored originals.
+- Healthy dictation reaches the existing one-minute limit through stop/final-result collection, with a two-second release fallback and an accurate limit notice. Startup/service errors remain separate.
+- A local classic worker performs SheetJS parse/write operations. Each conversion owns its worker and releases it on completion, failure, cancellation or timeout. Caller-owned buffers stay intact. Main-thread text decoding retains existing encoding behavior; browsers without Worker retain the old compatibility path. Both worker and SheetJS are precached for first offline use.
+- Conversation saves reuse validated serialization only for owned, deeply frozen plain-data snapshots. External mutable records and exotic mutable objects remain fully processed. Database schema and revision conflict guards are unchanged.
+
+## Verification
+
+- Confirmed RED regressions before fixes for save state, control recovery, history focus/stale results, chat conflicts and dictation duration.
+- Full unit coverage: **6,844 tests in 256 files passed**. Statements 88.55%, branches 84.34%, functions 89.91%, lines 91.06%; configured package thresholds passed.
+- Workspace types/lint, formatting and production build passed. Both archive gates verified 1,511 immutable evaluation artifacts.
+- Real SheetJS VM tests round-trip Chinese CSV and HTML tables through XLSX and BOM-prefixed CSV without a DOM.
+- Chromium production-build acceptance: **37 tests passed** (2.8 minutes), covering four-editor dictation, history actions/rendering, local document history keyboard focus, failed-open recovery, CSV encodings, responsive 50,000-row worker conversion and first offline conversion.
+
+## Repeated-save benchmark
+
+Node/Vitest with fake IndexedDB, 20 messages of roughly 1 KB each per conversation. Initial save and snapshot preparation are excluded; each sample changes one conversation. Five repeated saves per configuration, median elapsed time:
+
+| Conversations | Mutable snapshots | Prepared immutable snapshots |
+| ------------- | ----------------: | ---------------------------: |
+| 100           |           1.19 ms |                      0.18 ms |
+| 1,000         |          11.09 ms |                      0.60 ms |
+
+This measures reduced repeated serialization work in a controlled harness, not browser disk latency or model first-token time. A deterministic regression also asserts that unchanged prepared records are not serialized again. First history loading still reads all conversation bodies.
+
+## Limits and follow-ups
+
+Physical microphone recognition and actual GPU generation latency were not measured. CPU-model cancellation teardown and the existing full-format offline preparation contract remain unchanged. They require separate lifecycle/network measurements before changing their guarantees. The worker improves responsiveness, not necessarily total conversion duration; decoding still runs on the main thread. Conflict recovery copies remain in memory until saving is explicitly re-enabled.
+
+Source and caller review covered save ownership, stale view results, conflict-copy ownership, mutable external records, worker cleanup and static offline dependencies.
+
+## Follow-up review
+
+A second pass over this branch found two problems in how the new SheetJS worker
+ships. Neither affects the conversion logic.
+
+### The worker was served stale after a deploy
+
+`public/libs/sheetjs/convert.worker.js` has a fixed name, and its message
+protocol (`operation`, `data`, `{ ok, data | error }`) changes with the app
+bundle that posts to it.
+
+- **Before:** the Service Worker precached it into the runtime cache and served
+  it stale-while-revalidate. The first CSV or HTML-table conversion after a
+  deploy that changed the protocol would run against the previous worker. This
+  is the deploy-coupled case CLAUDE.md describes.
+- **After:** the worker is in `DEPLOY_COUPLED`, in the `public/_headers`
+  no-cache group, and in the core precache list. Network-first's offline
+  fallback reads only the core cache, so offline conversion keeps working.
+  `xlsx.full.min.js` rarely changes, so it stays stale-while-revalidate.
+- **Precache location:** both files are precached into the core cache. They are
+  not under the vendor trees (`sdkjs`, `web-apps`, `fonts`), so when a deploy
+  that leaves vendor unchanged activates with no window open,
+  `pruneAppAssets` would delete them from the runtime cache, and the first
+  offline CSV conversion would fail. The stale-while-revalidate branch reads
+  through `caches.match`, which also finds the core copy.
+- **Tests:** `sw-routing.test.ts` asserts network-first for the worker, and
+  `sw-boot-precache.test.ts` now records cache entries by cache name and asserts
+  the worker lands in core. Both fail with the previous `sw.js`.
+  `spreadsheet-worker.spec.ts`, including the first offline conversion, still
+  passes.
+
+### The worker was never linted
+
+- **Before:** `.oxlintrc.json` ignored `public/libs/**`, which took the
+  repository's own worker out of the lint along with the vendored bundle.
+- **After:** only `public/libs/sheetjs/xlsx.full.min.js` is ignored, and the
+  worker lints clean.
+- **Test:** `workflow-contract.test.ts` checks that `public/sw.js` and the
+  worker match no ignore pattern. It fails against the old configuration.
+
+### Checked and left as is
+
+`recoverSaved` compares the local and saved records with `JSON.stringify`. Both
+build their keys in the same order (`id, title, createdAt, updatedAt,
+messages`), and saving updates through an object spread that keeps that order.
+An unchanged conversation therefore never becomes a spurious local copy.
diff --git a/docs/superpowers/plans/2026-10-26-reliability-and-responsiveness.md b/docs/superpowers/plans/2026-10-26-reliability-and-responsiveness.md
new file mode 100644
index 000000000..02fbd0450
--- /dev/null
+++ b/docs/superpowers/plans/2026-10-26-reliability-and-responsiveness.md
@@ -0,0 +1,27 @@
+# Reliability and Responsiveness Implementation Plan
+
+> **For agentic workers:** REQUIRED: Use subagent-driven-development. Keep functional commits separate.
+
+**Goal:** Repair the five reviewed user-facing defects and improve measured responsiveness in one PR.
+**Architecture:** Keep save ownership, view state, conversation storage and conversion execution in their existing owners. Add narrowly scoped worker/view helpers where needed.
+**Tech Stack:** TypeScript, ranui, Vitest, Playwright, IndexedDB, browser Workers.
+
+## Chunk 1: Reliability
+
+- [x] Save semantics: `lib/onlyoffice/save-stream.ts`, `test/unit/save-stream-lifecycle.test.ts`. Assert exporting PDF retains dirty state before applying a regular-save-only completion guard. Run targeted tests and commit.
+- [x] Open recovery: `lib/ui.ts`, `styles/base.css`, focused unit/E2E tests. Cover hidden/pointer/timer races. Only activate hero layout when present; cancel stale timers and restore input. Commit.
+- [x] History view: `lib/history-page.ts`, focused tests. Keep toolbar stable, reject stale responses, prune on initialization rather than queries; validate keyboard focus and results. Commit.
+- [x] Chat conflicts: `lib/agent-plugin/ui/sessions.ts`, `history-controls.ts`, locales and tests. Explicit preserve-local recovery avoids repeated conflict and silent data loss. Validate two-store race, persisted restart and current conversation ownership. Commit.
+- [x] Speech duration: `lib/agent-plugin/ui/speech-input.ts`, locales and tests. Test healthy results at 59 seconds followed by duration limit. Graceful stop with bounded final-result drain and accurate notice. Commit.
+
+## Chunk 2: Responsiveness
+
+- [x] Spreadsheet worker: `packages/converter/src/spreadsheet.ts`, `document-converter.ts`, new worker/client helper and tests. Read converter rules first. Preserve CSV/HTML/XLSX conversion APIs, source ownership, CSP/static-host/offline behavior. Measure representative input; browser UI responsiveness must improve. Commit independently.
+- [x] Conversation persistence: inspect `conversation-db.ts` and `sessions.ts`. Benchmark 100/1000 conversations; apply safe incremental-processing optimization with invalidation tests. Avoid speculative storage migration. Commit independently if measured benefit justifies change.
+
+## Chunk 3: Delivery
+
+- [x] Specification review and source/caller quality review; resolve findings. Final independent agent review was unavailable due to tool-service errors; primary review completed.
+- [x] Run focused tests then full coverage, lint/types, format and production build. Only one browser/build runner.
+- [x] Real browser acceptance for opening failure, search focus, conversion and assistant flows. Document physical mic/GPU limits.
+- [ ] Update changelog and acceptance record. Push functional commits, create and attach one PR. Inspect exact-head checks and repair failures.
diff --git a/docs/superpowers/specs/2026-10-26-reliability-and-responsiveness-design.md b/docs/superpowers/specs/2026-10-26-reliability-and-responsiveness-design.md
new file mode 100644
index 000000000..a9e421f4d
--- /dev/null
+++ b/docs/superpowers/specs/2026-10-26-reliability-and-responsiveness-design.md
@@ -0,0 +1,25 @@
+# Reliability and responsiveness
+
+Implement the reviewed main-branch findings in one PR with independent functional commits.
+
+## Behavior
+
+1. Exporting another format does not mark the editable source saved. Normal saves retain existing version/ownership protections.
+2. Failed editor opens restore a visible, focusable file-opening control surface; stale visibility timers cannot hide it again.
+3. Document history keeps its toolbar/input mounted across searches, applies only current async results, and avoids pruning on every keystroke.
+4. A conflicting chat can explicitly preserve local work as a separate conversation and restore saved history. Preserve revision checks and active request ownership; never silently discard either copy.
+5. Healthy dictation ends gracefully at the duration limit. Startup/service failures remain distinct, and stop still has a bounded final-result wait.
+6. Move large spreadsheet conversions off the main thread with a bounded worker lifecycle, current-request ownership and unchanged conversion results. Do not introduce a dependency on remote scripts.
+7. Optimize history storage processing where safe without a data-format migration. Preserve cross-tab conflict detection and validate external records.
+
+CPU model restart and offline caching require benchmark-backed changes: retain cancellation teardown and first-offline-export contracts. Record measured limitations rather than promise unverified speedups.
+
+## Verification
+
+Regression tests must fail before fixes for the five confirmed bugs. Run relevant unit tests, full type/lint/format/coverage gates, production build and focused real-browser history/open/conversion/assistant acceptance. Run independent specification and code-quality reviews. Publish English PR text and preserve separate commits; do not merge.
+
+## Review constraints
+
+- Conflict recovery preserves all locally modified conversations, revalidates remote revisions and remains safe to retry without duplicate copies.
+- History expiry cleanup is throttled and runs on page restoration as well as initialization. Stale results never publish.
+- Worker load failure, timeout, cancellation and document replacement settle the caller and release resources. Offline manifests retain the worker and its local dependencies.
diff --git a/lib/agent-plugin/ui/conversation-db.ts b/lib/agent-plugin/ui/conversation-db.ts
index 4a60b70bd..9b98a277e 100644
--- a/lib/agent-plugin/ui/conversation-db.ts
+++ b/lib/agent-plugin/ui/conversation-db.ts
@@ -24,6 +24,30 @@ export interface ConversationRepository {
   clear(): Promise<number>;
 }
 
+// Only detached, recursively immutable plain data may skip repeated validation.
+// Object.freeze(Date/Map) does not freeze their contents: those remain uncached.
+const preparedRecords = new WeakMap<ConversationRecord, string>();
+function freezePlainData(value: unknown, seen = new WeakSet<object>()): boolean {
+  if (value === null || typeof value !== 'object') return true;
+  if (seen.has(value)) return true;
+  const prototype = Object.getPrototypeOf(value);
+  if (!Array.isArray(value) && prototype !== Object.prototype && prototype !== null) return false;
+  seen.add(value);
+  const plain = Object.values(value)
+    .map((child) => freezePlainData(child, seen))
+    .every(Boolean);
+  if (plain) Object.freeze(value);
+  return plain;
+}
+
+/** Prepare an owned snapshot once; arbitrary repository callers remain mutable. */
+export function prepareConversationRecord(record: ConversationRecord): ConversationRecord {
+  if (!isConversationRecord(record)) throw new Error('Saved conversation data is invalid');
+  const copy = structuredClone(normalizeRecord(record));
+  if (freezePlainData(copy)) preparedRecords.set(copy, JSON.stringify(copy));
+  return copy;
+}
+
 export const CONVERSATION_DB_NAME = 'document-ai-conversations';
 export function validConversationId(value: unknown): value is string {
   return typeof value === 'string' && /^(?:default|[a-f0-9-]{36})$/.test(value);
@@ -32,6 +56,7 @@ export function validConversationId(value: unknown): value is string {
 export function isConversationRecord(value: unknown): value is ConversationRecord {
   if (typeof value !== 'object' || value === null) return false;
   const item = value as ConversationRecord;
+  if (preparedRecords.has(item)) return true;
   return (
     validConversationId(item.id) &&
     typeof item.title === 'string' &&
@@ -42,7 +67,9 @@ export function isConversationRecord(value: unknown): value is ConversationRecor
   );
 }
 
-function normalizeRecord({ id, title, createdAt, updatedAt, messages }: ConversationRecord): ConversationRecord {
+function normalizeRecord(record: ConversationRecord): ConversationRecord {
+  if (preparedRecords.has(record)) return record;
+  const { id, title, createdAt, updatedAt, messages } = record;
   return { id, title, createdAt, updatedAt, messages };
 }
 
@@ -70,7 +97,9 @@ function validateStored(value: unknown): StoredConversations | null {
 
 export class ConversationConflictError extends Error {
   constructor() {
-    super('Saved conversations changed in another tab. Export this conversation before restoring saved history.');
+    super(
+      'Saved conversations changed in another tab. Keep local copies and restore saved history to preserve both versions.',
+    );
     this.name = 'ConversationConflictError';
   }
 }
@@ -214,7 +243,9 @@ export function createConversationRepository(): ConversationRepository {
             if ((index?.revision ?? 0) !== expectedRevision) throw new ConversationConflictError();
             // Normalize host records too, so unrelated properties never enter saved history.
             result = validateStored({ ...data, revision: (index?.revision ?? 0) + 1 })!;
-            serialized = new Map(result.sessions.map((item) => [item.id, JSON.stringify(item)]));
+            serialized = new Map(
+              result.sessions.map((item) => [item.id, preparedRecords.get(item) ?? JSON.stringify(item)]),
+            );
             const nextIds = new Set(serialized.keys());
             for (const id of index?.sessionIds ?? []) if (!nextIds.has(id)) sessions.delete(id);
             for (const item of result.sessions) {
diff --git a/lib/agent-plugin/ui/history-controls.ts b/lib/agent-plugin/ui/history-controls.ts
index dc104ad9a..9a92b3bac 100644
--- a/lib/agent-plugin/ui/history-controls.ts
+++ b/lib/agent-plugin/ui/history-controls.ts
@@ -65,6 +65,7 @@ export function createHistoryControls(options: HistoryControlsOptions) {
     return item;
   };
   const restore = button('agent-history-restore', 'M3 11a9 9 0 1 1 3 8M3 5v6h6M12 7v5l3 2');
+  const recover = button('agent-history-recover', 'M3 11a9 9 0 1 1 3 8M3 5v6h6');
   const legacy = button('agent-history-import', 'M12 3v12m-4-4 4 4 4-4M4 15v5h16v-5');
   const exported = button('agent-history-export', 'M12 15V3m-4 4 4-4 4 4M4 15v5h16v-5');
   const remove = button('agent-history-delete-current', 'M9 8l6 6m0-6-6 6M20 11a8 8 0 0 1-8 8H4v-8a8 8 0 0 1 16 0Z');
@@ -73,7 +74,7 @@ export function createHistoryControls(options: HistoryControlsOptions) {
     actionLabels.get(item)!.textContent = t(key);
   };
   actions.append(
-    Div().class('agent-history-transfer-actions').children(restore, legacy, exported).build(),
+    Div().class('agent-history-transfer-actions').children(restore, recover, legacy, exported).build(),
     Div().class('agent-history-danger-actions').children(remove, clear).build(),
   );
   const confirmation = document.createElement('div');
@@ -100,6 +101,8 @@ export function createHistoryControls(options: HistoryControlsOptions) {
     legend.textContent = t('agentHistoryDataControls');
     saveText.textContent = t('agentSaveHistory');
     labelAction(restore, 'agentRestoreHistory');
+    labelAction(recover, 'agentRecoverHistory');
+    recover.hidden = failure !== 'agentHistoryConflict';
     labelAction(legacy, 'agentImportHistory');
     labelAction(exported, 'agentExportHistory');
     labelAction(remove, 'agentDeleteConversation');
@@ -162,6 +165,16 @@ export function createHistoryControls(options: HistoryControlsOptions) {
         restoreView();
       }),
   );
+  recover.addEventListener('click', () => {
+    if (busy) return;
+    void run(async () => {
+      options.onBeforeRestore?.();
+      await store.recoverSaved(t('agentHistoryLocalCopy'));
+      localStorageSetItem(SAVE_PREFERENCE, 'false');
+      restoreView();
+      restore.focus();
+    });
+  });
   legacy.addEventListener(
     'click',
     () =>
diff --git a/lib/agent-plugin/ui/sessions.ts b/lib/agent-plugin/ui/sessions.ts
index 789a87e2e..52bc0958b 100644
--- a/lib/agent-plugin/ui/sessions.ts
+++ b/lib/agent-plugin/ui/sessions.ts
@@ -4,6 +4,7 @@ import { createHistoryStorage, type HistoryStorage } from './storage';
 import {
   ConversationConflictError,
   createConversationRepository,
+  prepareConversationRecord,
   validConversationId,
   type Conversation,
   type ConversationData,
@@ -43,6 +44,7 @@ export function createConversationStore(onChange?: () => void, options: Conversa
   let epoch = 0;
   let knownRevision: number | undefined;
   let memoryRevision = 0;
+  let historyGeneration = 0;
   let dirty = false;
   const touched = new Set<string>();
   const removed = new Set<string>();
@@ -101,7 +103,7 @@ export function createConversationStore(onChange?: () => void, options: Conversa
     sessions: sessions.map((item) => {
       let copy = detached.get(item);
       if (!copy) {
-        copy = structuredClone(item);
+        copy = prepareConversationRecord(item);
         detached.set(item, copy);
       }
       return copy;
@@ -191,7 +193,9 @@ export function createConversationStore(onChange?: () => void, options: Conversa
       .sort((a, b) => Number(b.id === active) - Number(a.id === active) || b.updatedAt - a.updatedAt);
   const history = (id = active): HistoryStorage => {
     if (!sessions.some((item) => item.id === id)) throw new Error('Unknown conversation');
+    const generation = historyGeneration;
     const save = (messages: LLMMessage[]) => {
+      if (generation !== historyGeneration) return;
       const item = sessions.find((item) => item.id === id);
       // A detached controller may finish after deletion. It must never resurrect history.
       if (!item) return;
@@ -271,6 +275,47 @@ export function createConversationStore(onChange?: () => void, options: Conversa
         lastError = undefined;
         mergeSaved(await repository.load());
       }),
+    // Explicit recovery keeps local variants in memory; saving remains opt-in.
+    // Do not mutate local state until the read succeeds. A later save still
+    // compares the loaded database revision, including races with another tab.
+    recoverSaved: (copyLabel = 'Local copy'): Promise<void> => {
+      saving = false;
+      savePending = false;
+      epoch++;
+      return enqueue(async () => {
+        const stored = await repository.load();
+        const merged = structuredClone(stored?.sessions ?? []);
+        const localIds = new Set<string>();
+        let nextActive = active;
+        for (const item of sessions) {
+          if (!touched.has(item.id) && savedIds.has(item.id)) continue;
+          if (!item.messages.length && !item.title && !touched.has(item.id)) continue;
+          const remote = merged.find((entry) => entry.id === item.id);
+          if (remote && JSON.stringify(remote) === JSON.stringify(item)) continue;
+          const copy = structuredClone(item);
+          if (remote) {
+            copy.id = crypto.randomUUID();
+            copy.title = `${copy.title || copyLabel} (${copyLabel})`;
+            if (active === item.id) nextActive = copy.id;
+          }
+          merged.push(copy);
+          localIds.add(copy.id);
+        }
+        if (!merged.length) merged.push(blankConversation());
+        sessions = merged;
+        active = merged.some((item) => item.id === nextActive) ? nextActive : merged[0].id;
+        knownRevision = stored?.revision ?? 0;
+        savedIds = new Set(stored?.sessions.map((item) => item.id) ?? []);
+        touched.clear();
+        for (const id of localIds) touched.add(id);
+        removed.clear();
+        dirty = localIds.size > 0;
+        memoryRevision++;
+        historyGeneration++;
+        lastError = undefined;
+        onChange?.();
+      });
+    },
     setSaving: async (enabled: boolean): Promise<void> => {
       if (!enabled) {
         saving = false;
diff --git a/lib/agent-plugin/ui/speech-input.ts b/lib/agent-plugin/ui/speech-input.ts
index eab5ad6cc..53610fdad 100644
--- a/lib/agent-plugin/ui/speech-input.ts
+++ b/lib/agent-plugin/ui/speech-input.ts
@@ -156,6 +156,7 @@ export function mountSpeechInput(chat: SpeechComposer, allowed: () => boolean) {
   });
   let stopping = false;
   let listening = false;
+  let limitReached = false;
   let recognition: Recognition | undefined;
   let busy = false;
   let original = '';
@@ -204,6 +205,7 @@ export function mountSpeechInput(chat: SpeechComposer, allowed: () => boolean) {
     busy = false;
     stopping = false;
     listening = false;
+    limitReached = false;
     pauseDisclosure();
     privacy.removeAttribute('open');
     notice = '';
@@ -224,11 +226,21 @@ export function mountSpeechInput(chat: SpeechComposer, allowed: () => boolean) {
     clearTimeout(deadline);
     // Some services never emit end after stop. Keep the visible transcript and
     // release the microphone rather than stranding an explicit send indefinitely.
-    deadline = setTimeout(() => close(false, false, true), 2000);
+    const finishWithoutEnd = () => {
+      const limited = limitReached;
+      close(false, false, true);
+      if (limited) {
+        status.textContent = t('agentSpeechLimit');
+        notice = status.textContent;
+        render();
+        showDisclosure();
+      }
+    };
+    deadline = setTimeout(finishWithoutEnd, 2000);
     try {
       recognition?.stop();
     } catch {
-      close(false, false, true);
+      finishWithoutEnd();
     }
     return pending;
   };
@@ -241,6 +253,7 @@ export function mountSpeechInput(chat: SpeechComposer, allowed: () => boolean) {
     notice = '';
     stopping = false;
     listening = false;
+    limitReached = false;
     pauseDisclosure();
     privacy.removeAttribute('open');
     const token = ++revision;
@@ -292,7 +305,7 @@ export function mountSpeechInput(chat: SpeechComposer, allowed: () => boolean) {
         status.textContent === t('agentSpeechListening') ||
         status.textContent === t('agentSpeechFinishing')
       ) {
-        status.textContent = transcript ? '' : t('agentSpeechNoResult');
+        status.textContent = limitReached ? t('agentSpeechLimit') : transcript ? '' : t('agentSpeechNoResult');
       }
       stopping = false;
       busy = false;
@@ -311,6 +324,11 @@ export function mountSpeechInput(chat: SpeechComposer, allowed: () => boolean) {
       }
       deadline = setTimeout(() => {
         if (token === revision && busy) {
+          if (listening) {
+            limitReached = true;
+            void finish();
+            return;
+          }
           close();
           status.textContent = t('agentSpeechFailed');
           notice = status.textContent;
diff --git a/lib/converter.ts b/lib/converter.ts
index 3e9315a0a..d76574704 100644
--- a/lib/converter.ts
+++ b/lib/converter.ts
@@ -32,8 +32,10 @@ export async function handleDocumentOperation(options: {
   file?: File;
   readonly?: boolean;
   isCurrent?: () => boolean;
+  signal?: AbortSignal;
 }): Promise<void> {
   try {
+    options.signal?.throwIfAborted();
     // The DocsAPI loader is no longer a render-blocking <script> in
     // index.html (it cost ~0.5 s of homepage LCP for visitors who never open
     // a document); every open path funnels through here, so load it on
@@ -63,7 +65,7 @@ export async function handleDocumentOperation(options: {
         // and open the resulting real XLSX; saves come back as .xlsx.
         const raw = new Uint8Array(await file.arrayBuffer());
         if (isHtmlDocument(raw)) {
-          const xlsxFile = await x2tConverter.convertHtmlTableToXlsx(raw, fileName);
+          const xlsxFile = await x2tConverter.convertHtmlTableToXlsx(raw, fileName, options.signal);
           binData = await xlsxFile.arrayBuffer();
           openFileType = 'xlsx';
         } else {
@@ -82,7 +84,7 @@ export async function handleDocumentOperation(options: {
         // to CSV in handleFileStreamMessage so the user still gets a .csv
         // out (GitHub #13/#33).
         const csvData = new Uint8Array(await file.arrayBuffer());
-        const xlsxFile = await x2tConverter.convertCsvToXlsx(csvData, fileName);
+        const xlsxFile = await x2tConverter.convertCsvToXlsx(csvData, fileName, options.signal);
         binData = await xlsxFile.arrayBuffer();
         openFileType = 'xlsx';
       } else {
diff --git a/lib/document.ts b/lib/document.ts
index cfa08add7..f38b52527 100644
--- a/lib/document.ts
+++ b/lib/document.ts
@@ -51,7 +51,7 @@ export const onCreateNew = async (ext: string, options?: { docId?: string }): Pr
     const fileName = 'Untitled' + ext;
     await loadEditorApi();
     opening.assertCurrent();
-    await handleDocumentOperation({ fileName, isNew: true, isCurrent: opening.isCurrent });
+    await handleDocumentOperation({ fileName, isNew: true, signal: opening.signal, isCurrent: opening.isCurrent });
     if (!commitDocumentOpen(operation)) return;
     setDocmentObj({ fileName, file: undefined });
     clearDocumentSession();
@@ -94,6 +94,7 @@ export const openLocalFile = async (
       fileName: file.name,
       isNew: false,
       readonly: options?.readonly,
+      signal: opening.signal,
       isCurrent: opening.isCurrent,
     });
     if (!commitDocumentOpen(operation)) throw new DOMException('Document open superseded', 'AbortError');
@@ -214,6 +215,7 @@ export const openDocumentFromUrl = async (
       fileName: finalFileName,
       isNew: false,
       readonly: options?.readonly,
+      signal: opening.signal,
       isCurrent: opening.isCurrent,
     });
     if (!commitDocumentOpen(operation)) throw new DOMException('Document open superseded', 'AbortError');
diff --git a/lib/embed-api.ts b/lib/embed-api.ts
index 4f86dcd83..d17a808c8 100644
--- a/lib/embed-api.ts
+++ b/lib/embed-api.ts
@@ -136,6 +136,7 @@ async function openFile(file: File, readonly = false): Promise<void> {
     file,
     isNew: false,
     readonly,
+    signal: opening.signal,
     isCurrent: opening.isCurrent,
   });
   if (!commitDocumentOpen(opening.id)) throw new DOMException('Document open superseded', 'AbortError');
diff --git a/lib/events.ts b/lib/events.ts
index a2377b891..cfb577070 100644
--- a/lib/events.ts
+++ b/lib/events.ts
@@ -47,7 +47,13 @@ export const events: Record<string, MessageHandler<any, unknown>> = {
       try {
         const file = await MessageCodec.decodeFileChunked(chunks);
         opening.assertCurrent();
-        await handleDocumentOperation({ file, fileName: file.name, isNew: false, isCurrent: opening.isCurrent });
+        await handleDocumentOperation({
+          file,
+          fileName: file.name,
+          isNew: false,
+          signal: opening.signal,
+          isCurrent: opening.isCurrent,
+        });
         if (commitDocumentOpen(opening.id)) {
           setDocmentObj({ fileName: file.name, file });
           clearDocumentSession();
diff --git a/lib/history-page.ts b/lib/history-page.ts
index 849400961..4fa8927f7 100644
--- a/lib/history-page.ts
+++ b/lib/history-page.ts
@@ -28,6 +28,10 @@ import { daysUntilExpiry, hasUnsavedWork, type HistoryDoc } from './history/type
 import { confirmDialog } from './confirm-dialog';
 
 const SEARCH_DEBOUNCE_MS = 200;
+const EXPIRY_SWEEP_INTERVAL_MS = 60_000;
+let renderRevision = 0;
+let lastSweepAt = -Infinity;
+let sweep: Promise<void> | undefined;
 
 let query = '';
 let page = 1;
@@ -217,9 +221,12 @@ function buildToolbar(refresh: () => void): HTMLElement {
     .attr('value', query)
     .on('input', (event: Event) => {
       const value = (event as CustomEvent<{ value?: string }>).detail?.value ?? '';
+      // Invalidate pending reads immediately, not only after the debounce.
+      renderRevision++;
+      query = value;
+      page = 1;
       window.clearTimeout(searchTimer);
       searchTimer = window.setTimeout(() => {
-        query = value;
         // A new search starts at the top; staying on page 4 of the previous
         // result set shows an empty page more often than not.
         page = 1;
@@ -293,53 +300,68 @@ function buildAutosaveToggle(refresh: () => void): HTMLElement {
     .build();
 }
 
-async function render(): Promise<void> {
-  // Sweep before reading: a row the user is shown must not be one the seven-day
-  // rule already deleted, and this page is the most likely thing to be open
-  // when that boundary is crossed.
-  await pruneExpired();
+async function sweepExpired(force: boolean): Promise<void> {
+  if (sweep) return sweep;
+  if (!force && Date.now() - lastSweepAt < EXPIRY_SWEEP_INTERVAL_MS) return;
+  sweep = pruneExpired().then(() => {
+    lastSweepAt = Date.now();
+  });
+  try {
+    await sweep;
+  } finally {
+    sweep = undefined;
+  }
+}
+
+async function render(forceSweep = false): Promise<void> {
+  const revision = ++renderRevision;
+  await sweepExpired(forceSweep);
+  if (revision !== renderRevision) return;
   const [{ items, total, page: current, pageSize }, usage] = await Promise.all([
     listDocs({ query, page, unsavedOnly }),
     historyUsage(),
   ]);
+  if (revision !== renderRevision) return;
   page = current;
   syncUrl();
 
   const pages = Math.max(1, Math.ceil(total / pageSize));
   const refresh = () => void render();
 
-  const header = Div()
-    .class('history-header')
-    .children(
-      // chip -> title -> intro: the homepage hero's own opening, so the page a
-      // visitor reaches from it is recognisably the same product rather than
-      // an admin screen that happens to share a header.
-      Div()
-        .class('history-chip')
-        .children(View('i').class('history-chip-dot').build(), View('span').text(t('historyChip')).build())
-        .build(),
-      Div()
-        .class('history-title-row')
-        .children(
-          View('h1').class('history-title').text(t('historyTitle')).build(),
-          Div()
-            .class('history-header-actions')
-            .children(
-              button(
-                t('historyBack'),
-                () => {
-                  // Back to the homepage the reader came from, not to English.
-                  window.location.href = localeHomePath(getLanguage());
-                },
-                { type: 'text', class: 'history-back' },
-              ),
-            )
-            .build(),
-        )
-        .build(),
-      View('p').class('history-intro').text(t('historyIntro')).build(),
-    )
-    .build();
+  const header =
+    root().querySelector<HTMLElement>('.history-header') ??
+    Div()
+      .class('history-header')
+      .children(
+        // chip -> title -> intro: the homepage hero's own opening, so the page a
+        // visitor reaches from it is recognisably the same product rather than
+        // an admin screen that happens to share a header.
+        Div()
+          .class('history-chip')
+          .children(View('i').class('history-chip-dot').build(), View('span').text(t('historyChip')).build())
+          .build(),
+        Div()
+          .class('history-title-row')
+          .children(
+            View('h1').class('history-title').text(t('historyTitle')).build(),
+            Div()
+              .class('history-header-actions')
+              .children(
+                button(
+                  t('historyBack'),
+                  () => {
+                    // Back to the homepage the reader came from, not to English.
+                    window.location.href = localeHomePath(getLanguage());
+                  },
+                  { type: 'text', class: 'history-back' },
+                ),
+              )
+              .build(),
+          )
+          .build(),
+        View('p').class('history-intro').text(t('historyIntro')).build(),
+      )
+      .build();
 
   const list = items.length
     ? Div()
@@ -368,6 +390,7 @@ async function render(): Promise<void> {
             ? button(
                 t('historyClearSearch'),
                 () => {
+                  window.clearTimeout(searchTimer);
                   query = '';
                   unsavedOnly = false;
                   page = 1;
@@ -402,66 +425,96 @@ async function render(): Promise<void> {
    * these are controls, not navigation) -- it falls to the bottom of the
    * column, which is where it already was.
    */
-  const rail = View('aside')
-    .class('history-rail')
-    .children(
-      // How much is being kept is a fact about the store, not about the
-      // search, so it sits at the top of the rail rather than beside the
-      // search box, where it competed with the filter for the same row.
-      Div()
-        .class('history-usage')
-        .text(
-          total
-            ? `${t('historyCount', { count: String(total) })} · ${t('historyUsage', { size: formatBytes(usage) })}`
-            : '',
-        )
-        .build(),
-      Div()
-        .class('history-rail-block')
-        .children(
-          Div().class('history-rail-label').text(t('historyRailSettings')).build(),
-          buildAutosaveToggle(refresh),
-          ...(isAutosaveEnabled()
-            ? []
-            : [Div().class('history-note history-note-warn').text(t('historyAutosaveOff')).build()]),
-          button(
-            t('historyClearAll'),
-            () => {
-              void confirmDialog({
-                title: t('historyClearTitle'),
-                body: t('historyClearConfirm'),
-                confirmLabel: t('historyClearAll'),
-                cancelLabel: t('historyCancel'),
-                danger: true,
-              }).then((ok) => (ok ? clearAllHistory().then(refresh) : undefined));
-            },
-            { native: true, id: 'history-clear-all', class: 'history-clear' },
-          ),
-        )
-        .build(),
+  const rail =
+    root().querySelector<HTMLElement>('.history-rail') ??
+    View('aside')
+      .class('history-rail')
+      .children(
+        // How much is being kept is a fact about the store, not about the
+        // search, so it sits at the top of the rail rather than beside the
+        // search box, where it competed with the filter for the same row.
+        Div()
+          .class('history-usage')
+          .text(
+            total
+              ? `${t('historyCount', { count: String(total) })} · ${t('historyUsage', { size: formatBytes(usage) })}`
+              : '',
+          )
+          .build(),
+        Div()
+          .class('history-rail-block')
+          .children(
+            Div().class('history-rail-label').text(t('historyRailSettings')).build(),
+            buildAutosaveToggle(refresh),
+            ...(isAutosaveEnabled()
+              ? []
+              : [Div().class('history-note history-note-warn').text(t('historyAutosaveOff')).build()]),
+            button(
+              t('historyClearAll'),
+              () => {
+                void confirmDialog({
+                  title: t('historyClearTitle'),
+                  body: t('historyClearConfirm'),
+                  confirmLabel: t('historyClearAll'),
+                  cancelLabel: t('historyCancel'),
+                  danger: true,
+                }).then((ok) => (ok ? clearAllHistory().then(refresh) : undefined));
+              },
+              { native: true, id: 'history-clear-all', class: 'history-clear' },
+            ),
+          )
+          .build(),
+        Div()
+          .class('history-rail-block')
+          .children(
+            Div().class('history-rail-label').text(t('historyRailRetention')).build(),
+            Div().class('history-note').text(t('historyRetention')).build(),
+            Div().class('history-note').text(t('historyNotBackup')).build(),
+          )
+          .build(),
+      )
+      .build();
+
+  const usageText = total
+    ? `${t('historyCount', { count: String(total) })} · ${t('historyUsage', { size: formatBytes(usage) })}`
+    : '';
+  rail.querySelector('.history-usage')!.textContent = usageText;
+  const autosave = rail.querySelector<HTMLInputElement>('#history-autosave')!;
+  autosave.checked = isAutosaveEnabled();
+  const warning = rail.querySelector('.history-note-warn');
+  if (autosave.checked) warning?.remove();
+  else if (!warning) {
+    rail
+      .querySelector('#history-clear-all')!
+      .before(Div().class('history-note history-note-warn').text(t('historyAutosaveOff')).build());
+  }
+
+  const existing = root().querySelector('.history-page');
+  if (existing) {
+    existing.querySelector('#history-list, #history-empty')!.replaceWith(list);
+    existing.querySelector('.history-pager')?.remove();
+    if (pages > 1) existing.append(buildPager(page, pages, refresh));
+  } else {
+    root().append(
       Div()
-        .class('history-rail-block')
+        .class('history-shell')
         .children(
-          Div().class('history-rail-label').text(t('historyRailRetention')).build(),
-          Div().class('history-note').text(t('historyRetention')).build(),
-          Div().class('history-note').text(t('historyNotBackup')).build(),
+          Div()
+            .class('history-page')
+            .children(header, buildToolbar(refresh), list, ...(pages > 1 ? [buildPager(page, pages, refresh)] : []))
+            .build(),
+          rail,
         )
         .build(),
-    )
-    .build();
-
-  const pageEl = Div()
-    .class('history-shell')
-    .children(
-      Div()
-        .class('history-page')
-        .children(header, buildToolbar(refresh), list, ...(pages > 1 ? [buildPager(page, pages, refresh)] : []))
-        .build(),
-      rail,
-    )
-    .build();
-
-  root().replaceChildren(pageEl);
+    );
+  }
+  const search = document.getElementById('history-search') as HTMLElement & { value: string };
+  // Leave the live input alone while typing: even assigning its current value
+  // can reset selection in a custom input's shadow root.
+  if (search.value !== query) search.setAttribute('value', query);
+  const filter = document.getElementById('history-filter-unsaved')!;
+  filter.classList.toggle('is-on', unsavedOnly);
+  filter.setAttribute('aria-pressed', String(unsavedOnly));
 }
 
 /**
@@ -493,4 +546,7 @@ function syncPageChrome(): void {
 applyDocumentLanguage();
 syncPageChrome();
 readUrl();
+window.addEventListener('pageshow', (event) => {
+  if (event.persisted) void render(true);
+});
 void render();
diff --git a/lib/onlyoffice/save-stream.ts b/lib/onlyoffice/save-stream.ts
index fe3d66cd4..f7524c9db 100644
--- a/lib/onlyoffice/save-stream.ts
+++ b/lib/onlyoffice/save-stream.ts
@@ -241,7 +241,8 @@ function routeSavedFile(file: File, state: ReturnType<typeof standaloneExportSta
     if (regularSave && isCurrent() && isSavePointCurrent(state.point)) await savedToDiskListener?.(file, isCurrent);
     // Clearing dirty also makes reload look safe. Retain the saved bytes before
     // publishing completion, then recheck for edits made while storage waited.
-    if (state.isCurrent() && commitSavePoint(state.point)) markDocumentSaved();
+    // A PDF or other-format export does not save the editable source.
+    if (regularSave && state.isCurrent() && commitSavePoint(state.point)) markDocumentSaved();
   };
 
   // Write back to the document's own file where that is possible, and download
diff --git a/lib/ui.ts b/lib/ui.ts
index 0a9ddc6cb..6d6cb243d 100644
--- a/lib/ui.ts
+++ b/lib/ui.ts
@@ -20,8 +20,8 @@ let landingHero: HTMLElement | null = null;
 const getLandingHero = (): HTMLElement | null => (landingHero ??= document.getElementById('landing-hero'));
 
 export const showLanding = (): void => {
-  document.body.classList.add('landing-active');
   const hero = getLandingHero();
+  document.body.classList.toggle('landing-active', !!hero);
   if (hero) hero.style.display = '';
 };
 
@@ -37,6 +37,7 @@ export const hideLanding = (): void => {
 // create* wrapper at boot, so in practice it is built up front; the laziness
 // just makes call order a non-issue.)
 let controlPanel: HTMLElement | null = null;
+let visibilityTimer: ReturnType<typeof setTimeout> | undefined;
 
 const getControlPanel = (): HTMLElement => (controlPanel ??= buildControlPanel());
 
@@ -45,12 +46,14 @@ export const hideControlPanel = (): void => {
   // Dismiss the crawlable landing hero with the panel.
   hideLanding();
 
+  clearTimeout(visibilityTimer);
   const panel = getControlPanel();
+  panel.inert = true;
   // Immediately disable pointer events to prevent blocking
   panel.style.pointerEvents = 'none';
   panel.style.opacity = '0';
   // Hide after transition for smooth animation
-  setTimeout(() => {
+  visibilityTimer = setTimeout(() => {
     panel.style.display = 'none';
   }, 300);
 };
@@ -65,10 +68,15 @@ export const showControlPanel = (): void => {
   // screen (index.ts sets it before the panel is built).
   document.body.classList.remove('opening-document');
 
+  clearTimeout(visibilityTimer);
   const panel = getControlPanel();
+  const hasHero = !!getLandingHero();
+  panel.inert = hasHero;
+  panel.style.pointerEvents = hasHero ? 'none' : 'auto';
   panel.style.display = 'flex';
-  setTimeout(() => {
+  visibilityTimer = setTimeout(() => {
     panel.style.opacity = '1';
+    if (!hasHero) panel.querySelector<HTMLElement>('#upload-button')?.focus();
   }, 10);
 };
 
diff --git a/packages/converter/src/document-converter.ts b/packages/converter/src/document-converter.ts
index 255989ea1..acc36d253 100644
--- a/packages/converter/src/document-converter.ts
+++ b/packages/converter/src/document-converter.ts
@@ -1,3 +1,4 @@
+import { runSpreadsheetWorker } from './spreadsheet-worker';
 import { createObjectURL, isZipContainer, scriptOnLoad } from 'ranuts/utils';
 import type {
   BinConversionResult,
@@ -458,13 +459,13 @@ export class X2TConverter {
    * Load xlsx library from local file
    */
   /** CSV in, a real XLSX File out; see ./spreadsheet.ts. */
-  async convertCsvToXlsx(csvData: Uint8Array, fileName: string): Promise<File> {
-    return convertCsvToXlsx(csvData, fileName);
+  async convertCsvToXlsx(csvData: Uint8Array, fileName: string, signal?: AbortSignal): Promise<File> {
+    return convertCsvToXlsx(csvData, fileName, signal);
   }
 
   /** An HTML table wearing a spreadsheet extension; see ./spreadsheet.ts. */
-  async convertHtmlTableToXlsx(htmlData: Uint8Array, fileName: string): Promise<File> {
-    return convertHtmlTableToXlsx(htmlData, fileName);
+  async convertHtmlTableToXlsx(htmlData: Uint8Array, fileName: string, signal?: AbortSignal): Promise<File> {
+    return convertHtmlTableToXlsx(htmlData, fileName, signal);
   }
 
   /**
@@ -740,7 +741,10 @@ export class X2TConverter {
   /**
    * Convert XLSX bytes to CSV bytes (UTF-8 with BOM) via SheetJS.
    */
-  async xlsxToCsvBytes(xlsxArray: Uint8Array): Promise<Uint8Array<ArrayBuffer>> {
+  async xlsxToCsvBytes(xlsxArray: Uint8Array, signal?: AbortSignal): Promise<Uint8Array<ArrayBuffer>> {
+    signal?.throwIfAborted();
+    if (typeof Worker !== 'undefined')
+      return new Uint8Array(await runSpreadsheetWorker('xlsx-to-csv', xlsxArray, signal));
     const XLSX = await loadXlsxLibrary();
     const workbook = XLSX.read(xlsxArray, { type: 'array' });
     const firstSheetName = workbook.SheetNames[0];
diff --git a/packages/converter/src/spreadsheet-worker.ts b/packages/converter/src/spreadsheet-worker.ts
new file mode 100644
index 000000000..629bd4259
--- /dev/null
+++ b/packages/converter/src/spreadsheet-worker.ts
@@ -0,0 +1,57 @@
+import { BASE_PATH } from '@ranuts/shared/document-utils';
+
+export type SpreadsheetOperation = 'csv-to-xlsx' | 'html-to-xlsx' | 'xlsx-to-csv';
+const CONVERSION_TIMEOUT_MS = 120_000;
+
+/** Own one worker per conversion so cancellation never interrupts another document. */
+export function runSpreadsheetWorker(
+  operation: SpreadsheetOperation,
+  input: string | Uint8Array,
+  signal?: AbortSignal,
+): Promise<ArrayBuffer> {
+  return new Promise((resolve, reject) => {
+    if (signal?.aborted) {
+      reject(signal.reason ?? new DOMException('Conversion canceled', 'AbortError'));
+      return;
+    }
+    let worker: Worker | undefined;
+    let timer: ReturnType<typeof setTimeout> | undefined;
+    let settled = false;
+    const finish = (error?: unknown, data?: ArrayBuffer) => {
+      if (settled) return;
+      settled = true;
+      clearTimeout(timer);
+      signal?.removeEventListener('abort', abort);
+      if (worker) {
+        worker.onmessage = null;
+        worker.onerror = null;
+        worker.onmessageerror = null;
+        worker.terminate();
+      }
+      if (error !== undefined) reject(error);
+      else resolve(data!);
+    };
+    const abort = () => finish(signal?.reason ?? new DOMException('Conversion canceled', 'AbortError'));
+    try {
+      worker = new Worker(`${BASE_PATH}libs/sheetjs/convert.worker.js`);
+      worker.onmessage = (event: MessageEvent) => {
+        const message = event.data;
+        if (message?.ok === true && message.data instanceof ArrayBuffer) finish(undefined, message.data);
+        else
+          finish(new Error(typeof message?.error === 'string' ? message.error : 'Invalid spreadsheet worker result'));
+      };
+      worker.onerror = (event) => {
+        event.preventDefault();
+        finish(new Error(event.message || 'Spreadsheet worker failed'));
+      };
+      worker.onmessageerror = () => finish(new Error('Unreadable spreadsheet worker result'));
+      signal?.addEventListener('abort', abort, { once: true });
+      timer = setTimeout(() => finish(new Error('Spreadsheet conversion timed out')), CONVERSION_TIMEOUT_MS);
+      // Never detach a caller's buffer, including subarray views shared with other work.
+      const data = typeof input === 'string' ? input : new Uint8Array(input).buffer;
+      worker.postMessage({ operation, data }, typeof data === 'string' ? [] : [data]);
+    } catch (error) {
+      finish(error);
+    }
+  });
+}
diff --git a/packages/converter/src/spreadsheet.ts b/packages/converter/src/spreadsheet.ts
index 914275562..ca279bd52 100644
--- a/packages/converter/src/spreadsheet.ts
+++ b/packages/converter/src/spreadsheet.ts
@@ -1,3 +1,4 @@
+import { runSpreadsheetWorker } from './spreadsheet-worker';
 import { decodeTextBytes } from 'ranuts/utils';
 import { BASE_PATH } from '@ranuts/shared/document-utils';
 
@@ -40,13 +41,19 @@ export async function loadXlsxLibrary(): Promise<any> {
 }
 
 /** CSV in, a real XLSX File out, because the engine will not read CSV. */
-export async function convertCsvToXlsx(csvData: Uint8Array, fileName: string): Promise<File> {
+export async function convertCsvToXlsx(csvData: Uint8Array, fileName: string, signal?: AbortSignal): Promise<File> {
   try {
+    signal?.throwIfAborted();
+    if (typeof Worker !== 'undefined') {
+      const bytes = await runSpreadsheetWorker('csv-to-xlsx', decodeTextBytes(csvData), signal);
+      return new File([bytes], fileName.replace(/\.csv$/i, '.xlsx'), { type: XLSX_MIME });
+    }
     const XLSX = await loadXlsxLibrary();
     const workbook = XLSX.read(decodeTextBytes(csvData), { type: 'string', raw: false });
     const xlsxBuffer = XLSX.write(workbook, { type: 'array', bookType: 'xlsx' });
     return new File([xlsxBuffer], fileName.replace(/\.csv$/i, '.xlsx'), { type: XLSX_MIME });
   } catch (error) {
+    if (signal?.aborted) throw signal.reason;
     throw new Error(
       `Failed to convert CSV to XLSX: ${error instanceof Error ? error.message : 'Unknown error'}. ` +
         'Please convert your CSV file to XLSX format manually and try again.',
@@ -59,14 +66,24 @@ export async function convertCsvToXlsx(csvData: Uint8Array, fileName: string): P
  * from web systems) into a real XLSX. SheetJS parses `<table>` markup
  * natively; x2t cannot import it at all.
  */
-export async function convertHtmlTableToXlsx(htmlData: Uint8Array, fileName: string): Promise<File> {
+export async function convertHtmlTableToXlsx(
+  htmlData: Uint8Array,
+  fileName: string,
+  signal?: AbortSignal,
+): Promise<File> {
   try {
+    signal?.throwIfAborted();
+    if (typeof Worker !== 'undefined') {
+      const bytes = await runSpreadsheetWorker('html-to-xlsx', decodeTextBytes(htmlData), signal);
+      return new File([bytes], fileName.replace(/\.[^.]+$/, '') + '.xlsx', { type: XLSX_MIME });
+    }
     const XLSX = await loadXlsxLibrary();
     const workbook = XLSX.read(decodeTextBytes(htmlData), { type: 'string', raw: false });
     if (!workbook.SheetNames || workbook.SheetNames.length === 0) throw new Error('no table found');
     const xlsxBuffer = XLSX.write(workbook, { type: 'array', bookType: 'xlsx' });
     return new File([xlsxBuffer], fileName.replace(/\.[^.]+$/, '') + '.xlsx', { type: XLSX_MIME });
   } catch (error) {
+    if (signal?.aborted) throw signal.reason;
     throw new Error(
       `Failed to convert HTML table to XLSX: ${error instanceof Error ? error.message : 'Unknown error'}. ` +
         'The file is an HTML page saved with a spreadsheet extension; open it in a spreadsheet application and save it as XLSX.',
diff --git a/packages/shared/src/i18n/messages/de.ts b/packages/shared/src/i18n/messages/de.ts
index 38c6c5aa4..8cb900d4f 100644
--- a/packages/shared/src/i18n/messages/de.ts
+++ b/packages/shared/src/i18n/messages/de.ts
@@ -32,6 +32,7 @@ export const de: Partial<I18nMessages> = {
   agentSpeechDenied: 'Mikrofonzugriff verweigert. Bitte in den Browsereinstellungen erlauben.',
   agentSpeechFailed: 'Erkennung fehlgeschlagen. Mikrofon, Sprache und Verbindung prüfen.',
   agentSpeechFinishing: 'Erkennung wird beendet…',
+  agentSpeechLimit: 'Die Diktierzeit ist abgelaufen. Sie können erneut starten.',
   agentSpeechUnsupported: 'Spracheingabe ist in diesem Browser nicht verfügbar.',
   agentDownloadIncomplete: 'Download unvollständig',
   agentModelInUse: 'Wird verwendet',
@@ -347,7 +348,9 @@ export const de: Partial<I18nMessages> = {
   agentHistorySaveFailed:
     'Der Verlauf konnte nicht gespeichert werden. Die Unterhaltung bleibt auf dieser Seite; exportieren Sie sie vor dem Schließen.',
   agentHistoryConflict:
-    'Ein anderer Tab hat den gespeicherten Verlauf geändert. Exportieren Sie diese Unterhaltung vor dem Wiederherstellen.',
+    'Ein anderer Tab hat den Verlauf geändert. Behalten Sie lokale Kopien und stellen Sie den Verlauf wieder her.',
+  agentRecoverHistory: 'Lokale Kopien behalten und wiederherstellen',
+  agentHistoryLocalCopy: 'Lokale Kopie',
   agentRestoreHistory: 'Gespeicherten Verlauf wiederherstellen',
   agentImportHistory: 'Früheren Chatverlauf importieren',
   agentExportHistory: 'Unterhaltungen exportieren',
diff --git a/packages/shared/src/i18n/messages/en.ts b/packages/shared/src/i18n/messages/en.ts
index 6df0965c5..e12a09ec5 100644
--- a/packages/shared/src/i18n/messages/en.ts
+++ b/packages/shared/src/i18n/messages/en.ts
@@ -28,6 +28,7 @@ export const en: I18nMessages = {
   agentSpeechDenied: 'Microphone permission denied. Allow access in browser settings.',
   agentSpeechFailed: 'Speech recognition failed. Check your microphone, language and connection, then retry.',
   agentSpeechFinishing: 'Finishing…',
+  agentSpeechLimit: 'Dictation limit reached. You can start again.',
   agentSpeechUnsupported: 'Voice input is unavailable in this browser.',
   agentDownloadIncomplete: 'Incomplete download',
   agentModelInUse: 'In use',
@@ -329,7 +330,9 @@ export const en: I18nMessages = {
   agentHistorySaving: 'Chat history saving is enabled on this device.',
   agentHistoryBusy: 'Updating chat history…',
   agentHistorySaveFailed: 'Could not save history. Your conversation remains in this page; export it before closing.',
-  agentHistoryConflict: 'Another tab changed saved history. Export this conversation before restoring saved history.',
+  agentHistoryConflict: 'Another tab changed saved history. Keep local copies and restore to preserve both versions.',
+  agentRecoverHistory: 'Keep local copies and restore',
+  agentHistoryLocalCopy: 'Local copy',
   agentRestoreHistory: 'Restore saved history',
   agentImportHistory: 'Import previous chat history',
   agentExportHistory: 'Export conversations',
diff --git a/packages/shared/src/i18n/messages/es.ts b/packages/shared/src/i18n/messages/es.ts
index ded8e467d..cfa79f9db 100644
--- a/packages/shared/src/i18n/messages/es.ts
+++ b/packages/shared/src/i18n/messages/es.ts
@@ -31,6 +31,7 @@ export const es: Partial<I18nMessages> = {
   agentSpeechDenied: 'Permiso del micrófono denegado. Actívalo en los ajustes del navegador.',
   agentSpeechFailed: 'Error de reconocimiento. Comprueba el micrófono, idioma y conexión.',
   agentSpeechFinishing: 'Finalizando…',
+  agentSpeechLimit: 'Se alcanzó el límite de dictado. Puedes volver a empezar.',
   agentSpeechUnsupported: 'Este navegador no admite entrada de voz.',
   agentDownloadIncomplete: 'Descarga incompleta',
   agentModelInUse: 'En uso',
@@ -336,7 +337,10 @@ export const es: Partial<I18nMessages> = {
   agentHistoryBusy: 'Actualizando el historial de chat…',
   agentHistorySaveFailed:
     'No se pudo guardar el historial. La conversación sigue en esta página; expórtala antes de cerrarla.',
-  agentHistoryConflict: 'Otra pestaña cambió el historial guardado. Exporta esta conversación antes de restaurarlo.',
+  agentHistoryConflict:
+    'Otra pestaña cambió el historial. Conserva copias locales y restaura para mantener ambas versiones.',
+  agentRecoverHistory: 'Conservar copias locales y restaurar',
+  agentHistoryLocalCopy: 'Copia local',
   agentRestoreHistory: 'Restaurar historial guardado',
   agentImportHistory: 'Importar historial de chat anterior',
   agentExportHistory: 'Exportar conversaciones',
diff --git a/packages/shared/src/i18n/messages/ja.ts b/packages/shared/src/i18n/messages/ja.ts
index c7fa93d99..28d80a68a 100644
--- a/packages/shared/src/i18n/messages/ja.ts
+++ b/packages/shared/src/i18n/messages/ja.ts
@@ -31,6 +31,7 @@ export const ja: Partial<I18nMessages> = {
   agentSpeechDenied: 'マイクの許可が拒否されました。ブラウザー設定で許可してください。',
   agentSpeechFailed: '認識に失敗しました。マイク、言語、接続を確認してください。',
   agentSpeechFinishing: '認識を終了中…',
+  agentSpeechLimit: '音声入力の制限時間に達しました。もう一度開始できます。',
   agentSpeechUnsupported: 'このブラウザーでは音声入力を利用できません。',
   agentDownloadIncomplete: 'ダウンロード未完了',
   agentModelInUse: '使用中',
@@ -333,7 +334,9 @@ export const ja: Partial<I18nMessages> = {
   agentHistoryBusy: 'チャット履歴を更新中…',
   agentHistorySaveFailed:
     '履歴を保存できませんでした。会話はこのページに残っています。閉じる前にエクスポートしてください。',
-  agentHistoryConflict: '別のタブで保存済み履歴が変更されました。復元する前に現在の会話をエクスポートしてください。',
+  agentHistoryConflict: '別のタブで履歴が変更されました。ローカルコピーを残して復元すると両方の版を保持できます。',
+  agentRecoverHistory: 'ローカルコピーを残して復元',
+  agentHistoryLocalCopy: 'ローカルコピー',
   agentRestoreHistory: '保存済み履歴を復元',
   agentImportHistory: '以前のチャット履歴をインポート',
   agentExportHistory: '会話をエクスポート',
diff --git a/packages/shared/src/i18n/messages/ko.ts b/packages/shared/src/i18n/messages/ko.ts
index 7bb10ff50..17528c134 100644
--- a/packages/shared/src/i18n/messages/ko.ts
+++ b/packages/shared/src/i18n/messages/ko.ts
@@ -31,6 +31,7 @@ export const ko: Partial<I18nMessages> = {
   agentSpeechDenied: '마이크 권한이 거부되었습니다. 브라우저 설정에서 허용하세요.',
   agentSpeechFailed: '음성 인식 실패. 마이크, 언어 및 연결을 확인하세요.',
   agentSpeechFinishing: '인식 완료 중…',
+  agentSpeechLimit: '음성 입력 제한 시간에 도달했습니다. 다시 시작할 수 있습니다.',
   agentSpeechUnsupported: '이 브라우저는 음성 입력을 지원하지 않습니다.',
   agentDownloadIncomplete: '다운로드 미완료',
   agentModelInUse: '사용 중',
@@ -324,7 +325,9 @@ export const ko: Partial<I18nMessages> = {
   agentHistorySaving: '이 기기에 채팅 기록을 저장합니다.',
   agentHistoryBusy: '채팅 기록 업데이트 중…',
   agentHistorySaveFailed: '기록을 저장하지 못했습니다. 대화는 페이지에 남아 있으니 닫기 전에 내보내세요.',
-  agentHistoryConflict: '다른 탭에서 저장된 기록이 변경되었습니다. 복원하기 전에 현재 대화를 내보내세요.',
+  agentHistoryConflict: '다른 탭에서 기록이 변경되었습니다. 로컬 사본을 유지하고 복원하면 두 버전을 보존합니다.',
+  agentRecoverHistory: '로컬 사본 유지 및 복원',
+  agentHistoryLocalCopy: '로컬 사본',
   agentRestoreHistory: '저장된 기록 복원',
   agentImportHistory: '이전 채팅 기록 가져오기',
   agentExportHistory: '대화 내보내기',
diff --git a/packages/shared/src/i18n/messages/pt.ts b/packages/shared/src/i18n/messages/pt.ts
index 166e59206..2b0773444 100644
--- a/packages/shared/src/i18n/messages/pt.ts
+++ b/packages/shared/src/i18n/messages/pt.ts
@@ -30,6 +30,7 @@ export const pt: Partial<I18nMessages> = {
   agentSpeechDenied: 'Permissão do microfone negada. Permita o acesso nas configurações do navegador.',
   agentSpeechFailed: 'Falha no reconhecimento. Verifique microfone, idioma e conexão.',
   agentSpeechFinishing: 'Finalizando…',
+  agentSpeechLimit: 'O limite de ditado foi atingido. Pode começar novamente.',
   agentSpeechUnsupported: 'Este navegador não suporta entrada de voz.',
   agentDownloadIncomplete: 'Download incompleto',
   agentModelInUse: 'Em uso',
@@ -333,7 +334,9 @@ export const pt: Partial<I18nMessages> = {
   agentHistorySaveFailed:
     'Não foi possível guardar o histórico. A conversa continua nesta página; exporte-a antes de fechar.',
   agentHistoryConflict:
-    'Outro separador alterou o histórico guardado. Exporte esta conversa antes de restaurar o histórico.',
+    'Outro separador alterou o histórico. Mantenha cópias locais e restaure para preservar ambas as versões.',
+  agentRecoverHistory: 'Manter cópias locais e restaurar',
+  agentHistoryLocalCopy: 'Cópia local',
   agentRestoreHistory: 'Restaurar histórico guardado',
   agentImportHistory: 'Importar histórico de chat anterior',
   agentExportHistory: 'Exportar conversas',
diff --git a/packages/shared/src/i18n/messages/zh-CN.ts b/packages/shared/src/i18n/messages/zh-CN.ts
index 01ae562db..fdd018e1e 100644
--- a/packages/shared/src/i18n/messages/zh-CN.ts
+++ b/packages/shared/src/i18n/messages/zh-CN.ts
@@ -27,6 +27,7 @@ export const zhCN: I18nMessages = {
   agentSpeechDenied: '麦克风权限被拒绝，请在浏览器设置中允许访问。',
   agentSpeechFailed: '语音识别失败，请检查麦克风、语言和网络后重试。',
   agentSpeechFinishing: '正在完成识别…',
+  agentSpeechLimit: '已达到单次听写时长，可以继续听写。',
   agentSpeechUnsupported: '当前浏览器不支持语音输入。',
   agentDownloadIncomplete: '下载未完成',
   agentModelInUse: '正在使用',
@@ -311,7 +312,9 @@ export const zhCN: I18nMessages = {
   agentHistorySaving: '已开启此设备的聊天记录保存。',
   agentHistoryBusy: '正在更新聊天记录…',
   agentHistorySaveFailed: '无法保存记录。当前对话仍在页面中，关闭前请先导出。',
-  agentHistoryConflict: '其他页面已修改保存的记录。恢复前请先导出当前对话。',
+  agentHistoryConflict: '其他页面已修改保存的记录。可保留本地副本并恢复，两个版本都会保留。',
+  agentRecoverHistory: '保留本地副本并恢复',
+  agentHistoryLocalCopy: '本地副本',
   agentRestoreHistory: '恢复已保存的记录',
   agentImportHistory: '导入旧版聊天记录',
   agentExportHistory: '导出对话',
diff --git a/packages/shared/src/i18n/types.ts b/packages/shared/src/i18n/types.ts
index 5de8d7f44..210ab36f3 100644
--- a/packages/shared/src/i18n/types.ts
+++ b/packages/shared/src/i18n/types.ts
@@ -26,6 +26,7 @@ export interface I18nMessages {
   agentSpeechDenied: string;
   agentSpeechFailed: string;
   agentSpeechFinishing: string;
+  agentSpeechLimit: string;
   agentSpeechUnsupported: string;
 
   agentDownloadIncomplete: string;
@@ -322,6 +323,8 @@ export interface I18nMessages {
   agentHistoryBusy: string;
   agentHistorySaveFailed: string;
   agentHistoryConflict: string;
+  agentRecoverHistory: string;
+  agentHistoryLocalCopy: string;
   agentRestoreHistory: string;
   agentImportHistory: string;
   agentExportHistory: string;
diff --git a/public/_headers b/public/_headers
index 8ee2c0685..5887d99dd 100644
--- a/public/_headers
+++ b/public/_headers
@@ -47,6 +47,8 @@
   Cache-Control: no-cache
 /ranui-iife/*
   Cache-Control: no-cache
+/libs/sheetjs/convert.worker.js
+  Cache-Control: no-cache
 
 # Self-hosted fonts: unhashed but they only change with a ranui release; a
 # week of browser cache with revalidation after is a fine trade.
diff --git a/public/libs/sheetjs/convert.worker.js b/public/libs/sheetjs/convert.worker.js
new file mode 100644
index 000000000..111ce13fb
--- /dev/null
+++ b/public/libs/sheetjs/convert.worker.js
@@ -0,0 +1,31 @@
+/* Local-only SheetJS conversion. One request per worker; the owner terminates it. */
+self.onmessage = function (event) {
+  try {
+    var request = event.data;
+    if (
+      !request ||
+      !['csv-to-xlsx', 'html-to-xlsx', 'xlsx-to-csv'].includes(request.operation) ||
+      (request.operation === 'xlsx-to-csv' ? !(request.data instanceof ArrayBuffer) : typeof request.data !== 'string')
+    )
+      throw new Error('Invalid spreadsheet conversion request');
+    importScripts(new URL('./xlsx.full.min.js', self.location.href).href);
+    var binary = request.operation === 'xlsx-to-csv';
+    var workbook = XLSX.read(binary ? new Uint8Array(request.data) : request.data, {
+      type: binary ? 'array' : 'string',
+      ...(binary ? {} : { raw: false }),
+    });
+    if (!workbook.SheetNames || !workbook.SheetNames.length) throw new Error('no table found');
+    var output;
+    if (binary) {
+      var text = XLSX.utils.sheet_to_csv(workbook.Sheets[workbook.SheetNames[0]]);
+      var bytes = new TextEncoder().encode(text);
+      var csv = new Uint8Array(bytes.length + 3);
+      csv.set([0xef, 0xbb, 0xbf]);
+      csv.set(bytes, 3);
+      output = csv.buffer;
+    } else output = XLSX.write(workbook, { type: 'array', bookType: 'xlsx' });
+    self.postMessage({ ok: true, data: output }, [output]);
+  } catch (error) {
+    self.postMessage({ ok: false, error: error instanceof Error ? error.message : 'Spreadsheet conversion failed' });
+  }
+};
diff --git a/public/sw.js b/public/sw.js
index 4301696a6..dafac145c 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -32,6 +32,10 @@ const ASSETS_TO_CACHE = [
   './editor.html',
   './manifest.json',
   './theme-presentation.js',
+  // CSV and HTML-table opens convert through these. Not vendor assets, so the
+  // runtime cache's activation prune would drop them; core keeps them offline.
+  './libs/sheetjs/convert.worker.js',
+  './libs/sheetjs/xlsx.full.min.js',
   './icons/document-light.svg',
   './icons/document-dark.svg',
   './icons/document-light-32.png',
@@ -69,7 +73,7 @@ const EDITOR_BOOTSTRAP_HTML = [
 // its content changed.) Network-first with `cache: 'no-cache'` is what the HTML branch already
 // does, for exactly the same reason.
 const DEPLOY_COUPLED =
-  /^\/(?:home|landing|app-tokens)\.css$|^\/(?:lang-switch|sw-register|open-local|landing-prefetch|history-recent|theme-presentation)\.js$|^\/ranui-iife\//;
+  /^\/(?:home|landing|app-tokens)\.css$|^\/(?:lang-switch|sw-register|open-local|landing-prefetch|history-recent|theme-presentation)\.js$|^\/ranui-iife\/|^\/libs\/sheetjs\/convert\.worker\.js$/;
 
 // The OnlyOffice 9 tree is ~2600 files, but most of that is per-locale help
 // and on-demand font duplication a single session in one language never
diff --git a/test/e2e/entry-paths.spec.ts b/test/e2e/entry-paths.spec.ts
index 51089d6f6..059f5b2ba 100644
--- a/test/e2e/entry-paths.spec.ts
+++ b/test/e2e/entry-paths.spec.ts
@@ -28,7 +28,7 @@ test.beforeAll(async () => {
       res.end(Buffer.from(DOC));
       return;
     }
-    res.writeHead(404);
+    res.writeHead(404, { 'Access-Control-Allow-Origin': '*' });
     res.end();
   });
   await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve));
@@ -61,6 +61,28 @@ test.describe('entry paths (real editor)', () => {
     expect(ooxmlText((await zipEntryText(bytes, 'word/document.xml')) || '')).toContain('opened from a URL');
   });
 
+  test('a failed URL open restores keyboard-accessible local file controls', async ({ page, l0 }) => {
+    l0.allowConsole(/Error opening document from URL:.*Failed to fetch document: 404/);
+    const missing = new URL('/missing.docx', docUrl).href;
+    await page.goto(`/editor?file=${encodeURIComponent(missing)}`);
+    const upload = page.locator('#upload-button');
+    await expect(upload).toBeVisible();
+    await expect(upload).toBeFocused();
+    // Exercise the real control with the keyboard, then recover in the same page.
+    const chooser = page.waitForEvent('filechooser');
+    await page.keyboard.press('Enter');
+    await (
+      await chooser
+    ).setFiles({
+      name: 'recovered.docx',
+      mimeType: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+      buffer: Buffer.from(DOC),
+    });
+    await settleEditor(page);
+    await expect(page.frameLocator('iframe[name="frameEditor"]').locator('#editor_sdk')).toBeVisible();
+    await expect(page.locator('#control-panel-container')).toBeHidden();
+  });
+
   test('embed document:open-url fetches, opens and round-trips the document', async ({ page }) => {
     await page.goto('/embed-demo.html');
     await expect(page.locator('#status')).toHaveText('ready', { timeout: 60_000 });
diff --git a/test/e2e/history-page.spec.ts b/test/e2e/history-page.spec.ts
index 0ec4cdb3f..cf6e258f2 100644
--- a/test/e2e/history-page.spec.ts
+++ b/test/e2e/history-page.spec.ts
@@ -138,6 +138,26 @@ test.describe('local history page', () => {
     await expect(page.locator('#history-empty')).toBeVisible();
   });
 
+  test('keeps keyboard focus and the caret while search results refresh', async ({ page }) => {
+    await seed(page, [
+      { id: 'budget', title: 'Budget.docx' },
+      { id: 'other', title: 'Report.docx' },
+    ]);
+    await page.reload();
+    await expect(titles(page)).toHaveCount(2);
+    const input = page.locator('#history-search');
+    await input.click();
+    await page.keyboard.type('Bud');
+    await expect(titles(page)).toHaveText(['Budget.docx']);
+    await expect(input).toBeFocused();
+    // No re-click: the original shadow input must still own focus and caret.
+    await page.keyboard.type('get');
+    await expect(input).toHaveJSProperty('value', 'Budget');
+    await page.waitForURL(/q=Budget/);
+    await expect(titles(page)).toHaveText(['Budget.docx']);
+    await expect(input).toBeFocused();
+  });
+
   test('marks the rows whose only copy is in this browser', async ({ page }) => {
     await seed(page, [
       { id: 'only-here', title: 'OnlyHere.docx' },
diff --git a/test/e2e/spreadsheet-worker.spec.ts b/test/e2e/spreadsheet-worker.spec.ts
new file mode 100644
index 000000000..23ca62576
--- /dev/null
+++ b/test/e2e/spreadsheet-worker.spec.ts
@@ -0,0 +1,75 @@
+import { expect, test } from './lib/l0';
+
+test('large spreadsheet conversion leaves the main thread responsive and round trips Unicode', async ({ page }) => {
+  test.setTimeout(120_000);
+  await page.goto('/history');
+  const result = await page.evaluate(async () => {
+    const convert = (operation: string, data: string | ArrayBuffer): Promise<ArrayBuffer> =>
+      new Promise((resolve, reject) => {
+        const worker = new Worker('/libs/sheetjs/convert.worker.js');
+        worker.onmessage = (event) => {
+          worker.terminate();
+          if (event.data.ok) resolve(event.data.data);
+          else reject(new Error(event.data.error));
+        };
+        worker.onerror = (event) => {
+          worker.terminate();
+          reject(new Error(event.message));
+        };
+        worker.postMessage({ operation, data });
+      });
+    const input = 'name,value\n' + Array.from({ length: 50000 }, (_, i) => `项目${i},${i}`).join('\n');
+    let ticks = 0;
+    const timer = setInterval(() => ticks++, 10);
+    try {
+      const xlsx = await convert('csv-to-xlsx', input);
+      const conversionTicks = ticks;
+      const csv = new TextDecoder().decode(await convert('xlsx-to-csv', xlsx));
+      const html = await convert('html-to-xlsx', '<table><tr><td>中文</td><td>12</td></tr></table>');
+      return {
+        ticks: conversionTicks,
+        first: csv.includes('项目0,0'),
+        last: csv.includes('项目49999,49999'),
+        htmlBytes: html.byteLength,
+      };
+    } finally {
+      clearInterval(timer);
+    }
+  });
+  expect(result.ticks).toBeGreaterThan(1);
+  expect(result.first).toBe(true);
+  expect(result.last).toBe(true);
+  expect(result.htmlBytes).toBeGreaterThan(100);
+});
+
+test('first spreadsheet conversion is available offline after app preparation', async ({ page, context }) => {
+  test.setTimeout(120_000);
+  await page.goto('/');
+  await page.evaluate(async () => {
+    await navigator.serviceWorker.ready;
+  });
+  await page.reload();
+  await page.waitForFunction(() => !!navigator.serviceWorker.controller);
+  await context.setOffline(true);
+  try {
+    const magic = await page.evaluate(
+      () =>
+        new Promise<number[]>((resolve, reject) => {
+          const worker = new Worker('/libs/sheetjs/convert.worker.js');
+          worker.onmessage = (event) => {
+            worker.terminate();
+            if (!event.data.ok) reject(new Error(event.data.error));
+            else resolve([...new Uint8Array(event.data.data).slice(0, 2)]);
+          };
+          worker.onerror = (event) => {
+            worker.terminate();
+            reject(new Error(event.message));
+          };
+          worker.postMessage({ operation: 'csv-to-xlsx', data: 'name,value\n离线,12' });
+        }),
+    );
+    expect(magic).toEqual([0x50, 0x4b]);
+  } finally {
+    await context.setOffline(false);
+  }
+});
diff --git a/test/unit/agent-history-controls.test.ts b/test/unit/agent-history-controls.test.ts
index d6ded764e..01ee59122 100644
--- a/test/unit/agent-history-controls.test.ts
+++ b/test/unit/agent-history-controls.test.ts
@@ -359,3 +359,22 @@ it('settles clear-all exactly once only on successful retry while preserving con
   expect(restored).toHaveBeenCalledExactlyOnceWith('all');
   expect(document.activeElement).toBe(trigger);
 });
+
+it('offers explicit preserve-local recovery only after a conflict', async () => {
+  const store = createConversationStore();
+  store.history().save([{ role: 'user', content: 'local' }]);
+  const before = vi.fn();
+  const restored = vi.fn();
+  const controls = createHistoryControls({ store, onBeforeRestore: before, onRestore: restored });
+  document.body.append(controls.el);
+  const recover = controls.el.querySelector<HTMLButtonElement>('.agent-history-recover')!;
+  expect(recover.hidden).toBe(true);
+  controls.showError(new ConversationConflictError());
+  expect(recover.hidden).toBe(false);
+  recover.click();
+  await vi.waitFor(() => expect(restored).toHaveBeenCalledOnce());
+  expect(before).toHaveBeenCalledOnce();
+  expect(store.history().load()[0].content).toBe('local');
+  expect(store.saving).toBe(false);
+  expect(recover.hidden).toBe(true);
+});
diff --git a/test/unit/agent-sessions.test.ts b/test/unit/agent-sessions.test.ts
index d9f742bf4..a78e0867c 100644
--- a/test/unit/agent-sessions.test.ts
+++ b/test/unit/agent-sessions.test.ts
@@ -405,3 +405,56 @@ it('retains only explicitly owned volatile sessions while merging saved history'
   expect(store.activeId).toBe(savedId);
   expect(store.list().some((item) => item.id === initial)).toBe(false);
 });
+
+it('explicit conflict recovery preserves every local edit without overwriting saved originals', async () => {
+  const first = createConversationStore();
+  first.history().save([{ role: 'user', content: 'first original' }]);
+  const firstId = first.activeId;
+  const secondId = first.create().id;
+  first.history().save([{ role: 'user', content: 'second original' }]);
+  await first.setSaving(true);
+  const stale = createConversationStore();
+  await stale.restoreSaved();
+  await stale.setSaving(true);
+  first.history(firstId).save([{ role: 'user', content: 'remote edit' }]);
+  await first.flush();
+  stale.history(firstId).save([{ role: 'user', content: 'local first' }]);
+  stale.history(secondId).save([{ role: 'user', content: 'local second' }]);
+  await expect(stale.flush()).rejects.toThrow(/another tab/i);
+  const oldHandle = stale.history(firstId);
+  await stale.recoverSaved();
+  expect(stale.saving).toBe(false);
+  expect(stale.history(firstId).load()[0].content).toBe('remote edit');
+  expect(stale.history(secondId).load()[0].content).toBe('second original');
+  expect(stale.list()).toHaveLength(4);
+  const localIds = stale
+    .list()
+    .filter((item) => item.id !== firstId && item.id !== secondId)
+    .map((item) => item.id);
+  expect(localIds.map((id) => stale.history(id).load()[0].content).sort()).toEqual(['local first', 'local second']);
+  expect(localIds).toContain(stale.activeId);
+  oldHandle.save([{ role: 'assistant', content: 'late old controller' }]);
+  expect(stale.history(firstId).load()[0].content).toBe('remote edit');
+  await stale.recoverSaved();
+  expect(stale.list()).toHaveLength(4);
+  await stale.setSaving(true);
+  const restored = createConversationStore();
+  await restored.restoreSaved();
+  expect(restored.list()).toHaveLength(4);
+  expect(restored.history(firstId).load()[0].content).toBe('remote edit');
+});
+
+it('failed explicit recovery leaves local conversations intact for retry', async () => {
+  const repository = createConversationRepository();
+  const store = createConversationStore(undefined, { repository });
+  store.history().save([{ role: 'user', content: 'local work' }]);
+  const id = store.activeId;
+  const load = vi.spyOn(repository, 'load').mockRejectedValueOnce(new Error('Read unavailable'));
+  await expect(store.recoverSaved()).rejects.toThrow('Read unavailable');
+  expect(store.activeId).toBe(id);
+  expect(store.history().load()[0].content).toBe('local work');
+  load.mockRestore();
+  await store.recoverSaved();
+  expect(store.activeId).toBe(id);
+  expect(store.list()).toHaveLength(1);
+});
diff --git a/test/unit/agent-speech-input.test.ts b/test/unit/agent-speech-input.test.ts
index b2f4bd56c..81cfbfa1e 100644
--- a/test/unit/agent-speech-input.test.ts
+++ b/test/unit/agent-speech-input.test.ts
@@ -381,3 +381,30 @@ it('expires the error popover but retains the error and a readable detail entry'
     vi.useRealTimers();
   }
 });
+
+it.each(['end', 'timeout'] as const)('finishes healthy dictation at the duration limit (%s)', (ending) => {
+  vi.useFakeTimers();
+  try {
+    const { el, recognition, speech, draft } = setup();
+    recognition.onstart?.();
+    vi.advanceTimersByTime(59000);
+    recognition.onresult?.({ results: [{ isFinal: false, 0: { transcript: 'Visible words' } }] });
+    vi.advanceTimersByTime(1000);
+    expect(recognition.stop).toHaveBeenCalledOnce();
+    expect(recognition.abort).not.toHaveBeenCalled();
+    expect(speech.isBusy()).toBe(true);
+    if (ending === 'end') {
+      recognition.onresult?.({ results: [{ isFinal: true, 0: { transcript: 'Final words' } }] });
+      recognition.onend?.();
+    } else vi.advanceTimersByTime(2000);
+    expect(speech.isBusy()).toBe(false);
+    expect(draft()).toBe(ending === 'end' ? 'Original Final words' : 'Original Visible words');
+    expect(el.querySelector('[role="status"]')!.textContent).toBe('agentSpeechLimit');
+    el.querySelector<HTMLButtonElement>('.agent-speech-mic')!.click();
+    expect(speech.isBusy()).toBe(true);
+    expect(el.querySelector('[role="status"]')!.textContent).toBe('agentSpeechStarting');
+    speech.close();
+  } finally {
+    vi.useRealTimers();
+  }
+});
diff --git a/test/unit/control-panel-recovery.test.ts b/test/unit/control-panel-recovery.test.ts
new file mode 100644
index 000000000..6fc18a6f4
--- /dev/null
+++ b/test/unit/control-panel-recovery.test.ts
@@ -0,0 +1,71 @@
+import 'ranui/button';
+import { afterEach, beforeEach, expect, it, vi } from 'vitest';
+
+vi.mock('../../lib/prefetch', () => ({ prefetchOnIntent: vi.fn() }));
+vi.mock('../../lib/document', () => ({ onCreateNew: vi.fn(), onOpenDocument: vi.fn() }));
+vi.mock('../../lib/loading', () => ({ showLoading: () => ({ removeLoading: vi.fn() }) }));
+vi.mock('@ranuts/shared/i18n', () => ({ t: (key: string) => key }));
+
+beforeEach(() => {
+  vi.resetModules();
+  vi.useFakeTimers();
+  document.body.replaceChildren();
+  document.body.className = '';
+});
+afterEach(() => {
+  vi.clearAllTimers();
+  vi.useRealTimers();
+  document.body.replaceChildren();
+});
+
+it('restores the editor opening controls without activating a missing landing hero', async () => {
+  const ui = await import('../../lib/ui');
+  document.body.classList.add('opening-document');
+  ui.hideControlPanel();
+  vi.advanceTimersByTime(300);
+  ui.showControlPanel();
+  vi.advanceTimersByTime(10);
+  const panel = document.getElementById('control-panel-container')!;
+  expect(document.body.classList.contains('landing-active')).toBe(false);
+  expect(document.body.classList.contains('opening-document')).toBe(false);
+  expect(panel.style.display).toBe('flex');
+  expect(panel.style.opacity).toBe('1');
+  expect(panel.inert).toBe(false);
+  expect(panel.style.pointerEvents).not.toBe('none');
+  expect(document.activeElement).toBe(document.getElementById('upload-button'));
+});
+
+it('does not let an earlier hide timer hide controls after a quick open failure', async () => {
+  const ui = await import('../../lib/ui');
+  ui.hideControlPanel();
+  vi.advanceTimersByTime(100);
+  ui.showControlPanel();
+  vi.advanceTimersByTime(300);
+  expect(document.getElementById('control-panel-container')!.style.display).toBe('flex');
+});
+
+it('keeps hidden controls inert and ignores a superseded show transition', async () => {
+  const ui = await import('../../lib/ui');
+  ui.showControlPanel();
+  ui.hideControlPanel();
+  vi.advanceTimersByTime(20);
+  const panel = document.getElementById('control-panel-container')!;
+  expect(panel.style.opacity).toBe('0');
+  expect(panel.inert).toBe(true);
+  vi.advanceTimersByTime(300);
+  expect(panel.style.display).toBe('none');
+});
+
+it('restores a real landing hero without exposing or focusing duplicate controls', async () => {
+  const hero = document.createElement('main');
+  hero.id = 'landing-hero';
+  document.body.append(hero);
+  const ui = await import('../../lib/ui');
+  ui.hideControlPanel();
+  ui.showControlPanel();
+  vi.advanceTimersByTime(400);
+  expect(document.body.classList.contains('landing-active')).toBe(true);
+  expect(hero.style.display).toBe('');
+  expect(document.getElementById('control-panel-container')!.inert).toBe(true);
+  expect(document.activeElement).not.toBe(document.getElementById('upload-button'));
+});
diff --git a/test/unit/conversation-db.test.ts b/test/unit/conversation-db.test.ts
index b4f052a8b..166baf87e 100644
--- a/test/unit/conversation-db.test.ts
+++ b/test/unit/conversation-db.test.ts
@@ -4,6 +4,7 @@ import { beforeEach, expect, it, vi } from 'vitest';
 import {
   CONVERSATION_DB_NAME,
   createConversationRepository,
+  prepareConversationRecord,
   type ConversationData,
 } from '../../lib/agent-plugin/ui/conversation-db';
 
@@ -292,3 +293,57 @@ it('a racing erase cannot be undone by a save from the previous revision', async
   expect(erased?.revision).toBeGreaterThanOrEqual(2);
   await expect(writer.save(data, 1)).rejects.toThrow(/another tab/i);
 });
+
+it('reuses only owned immutable prepared records across saves', async () => {
+  const repository = createConversationRepository();
+  const original = structuredClone(data.sessions[0]);
+  const prepared = prepareConversationRecord(original);
+  original.messages[0].content = 'changed outside';
+  expect(prepared.messages[0].content).toBe('private');
+  expect(() => {
+    prepared.messages[0].content = 'mutated';
+  }).toThrow();
+  const stringify = vi.spyOn(JSON, 'stringify');
+  try {
+    await repository.save({ ...data, sessions: [prepared] }, 0);
+    await repository.save({ ...data, sessions: [prepared] }, 1);
+    expect(stringify).not.toHaveBeenCalled();
+    const changed = prepareConversationRecord({ ...prepared, title: 'new title' });
+    await repository.save({ ...data, sessions: [changed] }, 2);
+    expect(stringify).toHaveBeenCalledOnce();
+  } finally {
+    stringify.mockRestore();
+  }
+  expect((await repository.load())?.sessions[0].title).toBe('new title');
+});
+
+it('never trusts identity caching for mutable external records', async () => {
+  const repository = createConversationRepository();
+  const mutable = structuredClone(data);
+  await repository.save(mutable, 0);
+  mutable.sessions[0].messages[0].content = 'nested change';
+  await repository.save(mutable, 1);
+  expect((await repository.load())?.sessions[0].messages[0].content).toBe('nested change');
+});
+
+it('does not brand mutable exotic objects as immutable prepared data', async () => {
+  const repository = createConversationRepository();
+  const record = prepareConversationRecord({
+    ...data.sessions[0],
+    messages: [
+      { role: 'assistant', content: [{ type: 'tool_use', id: 'tool', name: 'read', input: { date: new Date(0) } }] },
+    ],
+  });
+  await repository.save({ ...data, sessions: [record] }, 0);
+  const blocks = record.messages[0].content;
+  if (typeof blocks === 'string' || blocks[0].type !== 'tool_use') throw new Error('Expected tool input');
+  const date = blocks[0].input.date;
+  if (!(date instanceof Date)) throw new Error('Expected a Date');
+  date.setTime(1000);
+  await repository.save({ ...data, sessions: [record] }, 1);
+  const saved = (await repository.load())!.sessions[0].messages[0].content;
+  if (typeof saved === 'string' || saved[0].type !== 'tool_use') throw new Error('Expected saved tool input');
+  const savedDate = saved[0].input.date;
+  expect(savedDate).toBeInstanceOf(Date);
+  expect((savedDate as Date).getTime()).toBe(1000);
+});
diff --git a/test/unit/converter-open-currency.test.ts b/test/unit/converter-open-currency.test.ts
index 076a5d043..2b51779db 100644
--- a/test/unit/converter-open-currency.test.ts
+++ b/test/unit/converter-open-currency.test.ts
@@ -47,3 +47,32 @@ describe('converter open currency', () => {
     expect(mount).not.toHaveBeenCalled();
   });
 });
+
+it('cancels spreadsheet preprocessing when another document takes over', async () => {
+  let worker!: { terminate: ReturnType<typeof vi.fn>; postMessage: ReturnType<typeof vi.fn> };
+  vi.stubGlobal(
+    'Worker',
+    class {
+      terminate = vi.fn();
+      postMessage = vi.fn();
+      constructor() {
+        worker = { terminate: this.terminate, postMessage: this.postMessage };
+      }
+    },
+  );
+  const alert = vi.spyOn(window, 'alert').mockImplementation(() => {});
+  const controller = new AbortController();
+  try {
+    const file = new File(['name,value\nitem,12'], 'old.csv');
+    const pending = handleDocumentOperation({ isNew: false, fileName: file.name, file, signal: controller.signal });
+    const rejected = expect(pending).rejects.toMatchObject({ name: 'AbortError' });
+    await vi.waitFor(() => expect(worker?.postMessage).toHaveBeenCalled());
+    controller.abort();
+    await rejected;
+    expect(worker.terminate).toHaveBeenCalledOnce();
+    expect(mount).not.toHaveBeenCalled();
+    expect(alert).not.toHaveBeenCalled();
+  } finally {
+    vi.unstubAllGlobals();
+  }
+});
diff --git a/test/unit/history-page-rendering.test.ts b/test/unit/history-page-rendering.test.ts
new file mode 100644
index 000000000..7a385c640
--- /dev/null
+++ b/test/unit/history-page-rendering.test.ts
@@ -0,0 +1,122 @@
+import { afterEach, beforeEach, expect, it, vi } from 'vitest';
+const store = vi.hoisted(() => ({ listDocs: vi.fn(), historyUsage: vi.fn(), pruneExpired: vi.fn() }));
+vi.mock('../../lib/history/store', () => ({
+  ...store,
+  clearAllHistory: vi.fn(),
+  deleteDoc: vi.fn(),
+  getLatestSnapshot: vi.fn(),
+}));
+vi.mock('../../lib/pending-open', () => ({ stashPendingFile: vi.fn() }));
+vi.mock('../../lib/confirm-dialog', () => ({ confirmDialog: vi.fn() }));
+vi.mock('@ranuts/shared/i18n', () => ({
+  applyDocumentLanguage: vi.fn(),
+  getLanguage: () => 'en',
+  localeHomePath: () => '/',
+  t: (key: string) => key,
+  withLocale: (url: string) => url,
+}));
+const result = (title: string) => ({
+  items: [{ id: title, title, ext: 'docx', updatedAt: Date.now(), size: 10 }],
+  total: 1,
+  page: 1,
+  pageSize: 20,
+});
+let removeListeners = () => {};
+beforeEach(() => {
+  vi.resetModules();
+  vi.useFakeTimers();
+  localStorage.clear();
+  document.body.innerHTML = '<div id="history-root"></div>';
+  window.history.replaceState(null, '', '/history');
+  store.listDocs.mockReset().mockResolvedValue(result('Initial.docx'));
+  store.historyUsage.mockReset().mockResolvedValue(10);
+  store.pruneExpired.mockReset().mockResolvedValue(undefined);
+  const listenerSpy = vi.spyOn(window, 'addEventListener');
+  removeListeners = () => {
+    for (const [name, handler] of listenerSpy.mock.calls) window.removeEventListener(name, handler);
+    listenerSpy.mockRestore();
+  };
+});
+afterEach(() => {
+  removeListeners();
+  vi.clearAllTimers();
+  vi.useRealTimers();
+});
+async function load() {
+  await import('../../lib/history-page');
+  await vi.advanceTimersByTimeAsync(0);
+}
+function input(value: string) {
+  const el = document.getElementById('history-search')!;
+  el.dispatchEvent(new CustomEvent('input', { detail: { value } }));
+  return el;
+}
+it('keeps the focused search host mounted across debounced results', async () => {
+  await load();
+  const search = input('Budget');
+  search.focus();
+  store.listDocs.mockResolvedValue(result('Budget.docx'));
+  await vi.advanceTimersByTimeAsync(200);
+  expect(document.getElementById('history-search')).toBe(search);
+  expect(document.activeElement).toBe(search);
+  expect(document.querySelector('.history-row-title')?.textContent).toBe('Budget.docx');
+  expect(store.pruneExpired).toHaveBeenCalledOnce();
+});
+it('invalidates an older result as soon as another query is typed, before debounce', async () => {
+  await load();
+  let finish!: (value: ReturnType<typeof result>) => void;
+  store.listDocs.mockImplementationOnce(
+    () =>
+      new Promise((resolve) => {
+        finish = resolve;
+      }),
+  );
+  input('Old');
+  await vi.advanceTimersByTimeAsync(200);
+  input('New');
+  finish(result('Old.docx'));
+  await vi.advanceTimersByTimeAsync(0);
+  expect(document.querySelector('.history-row-title')?.textContent).toBe('Initial.docx');
+  store.listDocs.mockResolvedValue(result('New.docx'));
+  await vi.advanceTimersByTimeAsync(200);
+  expect(document.querySelector('.history-row-title')?.textContent).toBe('New.docx');
+  expect(window.location.search).toBe('?q=New');
+});
+it('throttles expiry cleanup while refreshing it when the page returns', async () => {
+  await load();
+  input('A');
+  await vi.advanceTimersByTimeAsync(200);
+  input('B');
+  await vi.advanceTimersByTimeAsync(200);
+  expect(store.pruneExpired).toHaveBeenCalledOnce();
+  window.dispatchEvent(new PageTransitionEvent('pageshow', { persisted: true }));
+  await vi.advanceTimersByTimeAsync(0);
+  expect(store.pruneExpired).toHaveBeenCalledTimes(2);
+  await vi.advanceTimersByTimeAsync(60000);
+  input('C');
+  await vi.advanceTimersByTimeAsync(200);
+  expect(store.pruneExpired).toHaveBeenCalledTimes(3);
+});
+
+it('keeps the toolbar and settings interactive after filter and clear-search changes', async () => {
+  await load();
+  const toolbar = document.querySelector('.history-toolbar');
+  const toggle = document.querySelector<HTMLInputElement>('#history-autosave')!;
+  toggle.checked = false;
+  toggle.dispatchEvent(new Event('change'));
+  await vi.advanceTimersByTimeAsync(0);
+  expect(document.querySelector('#history-autosave')).toBe(toggle);
+  expect(document.querySelector('.history-note-warn')).not.toBeNull();
+  document.getElementById('history-filter-unsaved')!.click();
+  await vi.advanceTimersByTimeAsync(0);
+  expect(document.getElementById('history-filter-unsaved')!.getAttribute('aria-pressed')).toBe('true');
+  store.listDocs.mockResolvedValue({ items: [], total: 0, page: 1, pageSize: 20 });
+  input('Missing');
+  await vi.advanceTimersByTimeAsync(200);
+  document.querySelector<HTMLElement>('.history-empty-action')!.click();
+  await vi.advanceTimersByTimeAsync(0);
+  expect(document.querySelector('.history-toolbar')).toBe(toolbar);
+  expect(document.getElementById('history-search')!.getAttribute('value')).toBe('');
+  expect(document.getElementById('history-filter-unsaved')!.getAttribute('aria-pressed')).toBe('false');
+  expect(window.location.search).toBe('');
+});
diff --git a/test/unit/hosting-contract.test.ts b/test/unit/hosting-contract.test.ts
index 17f8d8459..af0ac5a0b 100644
--- a/test/unit/hosting-contract.test.ts
+++ b/test/unit/hosting-contract.test.ts
@@ -63,6 +63,8 @@ describe('public/_headers', () => {
       '/open-local.js',
       '/landing-prefetch.js',
       '/ranui-iife/*',
+      // Its message protocol changes with the app bundle that posts to it.
+      '/libs/sheetjs/convert.worker.js',
     ];
     for (const p of deployCoupled) {
       expect(cc(p), p).toBe('no-cache');
diff --git a/test/unit/save-stream-lifecycle.test.ts b/test/unit/save-stream-lifecycle.test.ts
index a09f2198c..3c5045b25 100644
--- a/test/unit/save-stream-lifecycle.test.ts
+++ b/test/unit/save-stream-lifecycle.test.ts
@@ -304,14 +304,20 @@ it('keeps a prior recovery point when saving the reload source fails', async ()
   expect(new Uint8Array(await opened.mock.calls[0][0].arrayBuffer())).toEqual(new Uint8Array([1]));
 });
 
-it('keeps the editable source after saving an export in another format', async () => {
+it('keeps the editable source unsaved after exporting another format', async () => {
   await rememberActiveSource('save-document', new File(['editable source'], 'Report.docx'));
-  setDiskWriter(async () => 'written');
+  const writer = vi.fn(async () => 'written' as const);
+  setDiskWriter(writer);
   await sendFile(true, 0, 'pdf');
-  await vi.waitFor(() => expect(hasUnsavedChanges()).toBe(false));
+  await vi.waitFor(() => expect(writer).toHaveBeenCalledOnce());
   await new Promise((resolve) => setTimeout(resolve, 30));
+  expect(hasUnsavedChanges()).toBe(true);
+  expect(history.Reset_SavedIndex).not.toHaveBeenCalled();
   expect(await (await readActiveSource('save-document'))?.text()).toBe('editable source');
   expect((await getDoc('save-document'))?.savedToDiskAt).toBeUndefined();
+  await sendFile();
+  await vi.waitFor(() => expect(hasUnsavedChanges()).toBe(false));
+  expect(history.Reset_SavedIndex).toHaveBeenCalledWith(true);
 });
 
 it('publishes save completion only after the saved reload bytes are durable', async () => {
diff --git a/test/unit/spreadsheet-worker-runtime.test.ts b/test/unit/spreadsheet-worker-runtime.test.ts
new file mode 100644
index 000000000..9b6fa6078
--- /dev/null
+++ b/test/unit/spreadsheet-worker-runtime.test.ts
@@ -0,0 +1,42 @@
+import { readFileSync } from 'node:fs';
+import { createContext, runInContext } from 'node:vm';
+import { expect, it } from 'vitest';
+
+function conversion(operation: string, data: string | ArrayBuffer) {
+  let response: { ok: boolean; data: ArrayBuffer; error?: string };
+  const context = createContext({
+    URL,
+    ArrayBuffer,
+    Uint8Array,
+    TextEncoder,
+    TextDecoder,
+    self: {
+      location: { href: 'https://example.com/document/libs/sheetjs/convert.worker.js' },
+      postMessage: (result: typeof response) => {
+        response = result;
+      },
+    },
+    importScripts: (url: string) => {
+      expect(url).toBe('https://example.com/document/libs/sheetjs/xlsx.full.min.js');
+      runInContext(readFileSync('public/libs/sheetjs/xlsx.full.min.js', 'utf8'), context);
+    },
+  });
+  runInContext(readFileSync('public/libs/sheetjs/convert.worker.js', 'utf8'), context);
+  context.self.onmessage({ data: { operation, data } });
+  return response!;
+}
+it.each([
+  ['csv-to-xlsx', 'name,value\n中文,12'],
+  ['html-to-xlsx', '<table><tr><td rowspan="2">中文</td><td>12</td></tr><tr><td>13</td></tr></table>'],
+])('converts %s and round trips text through the real local SheetJS worker', (operation, input) => {
+  const xlsx = conversion(operation, input);
+  expect(xlsx.ok).toBe(true);
+  expect([...new Uint8Array(xlsx.data).slice(0, 2)]).toEqual([0x50, 0x4b]);
+  const csv = conversion('xlsx-to-csv', xlsx.data);
+  expect(csv.ok).toBe(true);
+  expect([...new Uint8Array(csv.data).slice(0, 3)]).toEqual([0xef, 0xbb, 0xbf]);
+  expect(new TextDecoder().decode(csv.data)).toContain('中文,12');
+});
+it('returns a bounded error for malformed operations', () => {
+  expect(conversion('invalid', 'x')).toMatchObject({ ok: false, error: 'Invalid spreadsheet conversion request' });
+});
diff --git a/test/unit/spreadsheet-worker.test.ts b/test/unit/spreadsheet-worker.test.ts
new file mode 100644
index 000000000..f822274e4
--- /dev/null
+++ b/test/unit/spreadsheet-worker.test.ts
@@ -0,0 +1,62 @@
+import { afterEach, expect, it, vi } from 'vitest';
+import { runSpreadsheetWorker } from '../../packages/converter/src/spreadsheet-worker';
+class FakeWorker {
+  static current: FakeWorker;
+  onmessage: ((event: MessageEvent) => void) | null = null;
+  onerror: ((event: ErrorEvent) => void) | null = null;
+  onmessageerror: (() => void) | null = null;
+  postMessage = vi.fn();
+  terminate = vi.fn();
+  constructor(public url: string) {
+    FakeWorker.current = this;
+  }
+}
+function setup() {
+  vi.stubGlobal('Worker', FakeWorker);
+}
+afterEach(() => {
+  vi.unstubAllGlobals();
+  vi.useRealTimers();
+});
+it('transfers an exact copied view and terminates after a valid result', async () => {
+  setup();
+  const source = new Uint8Array([9, 1, 2, 9]);
+  const result = runSpreadsheetWorker('xlsx-to-csv', source.subarray(1, 3));
+  const worker = FakeWorker.current;
+  const [message, transfer] = worker.postMessage.mock.calls[0];
+  expect([...new Uint8Array(message.data)]).toEqual([1, 2]);
+  expect(transfer).toEqual([message.data]);
+  expect(source.byteLength).toBe(4);
+  worker.onmessage?.({ data: { ok: true, data: new Uint8Array([3]).buffer } } as MessageEvent);
+  expect([...new Uint8Array(await result)]).toEqual([3]);
+  expect(worker.terminate).toHaveBeenCalledOnce();
+});
+it.each(['abort', 'timeout', 'error', 'messageerror', 'invalid'] as const)(
+  'settles and releases a worker on %s',
+  async (reason) => {
+    setup();
+    vi.useFakeTimers();
+    const controller = new AbortController();
+    const result = runSpreadsheetWorker('csv-to-xlsx', 'a,b', controller.signal);
+    const rejected = expect(result).rejects.toBeInstanceOf(Error);
+    const worker = FakeWorker.current;
+    if (reason === 'abort') controller.abort();
+    if (reason === 'timeout') vi.advanceTimersByTime(120000);
+    if (reason === 'error') worker.onerror?.({ message: 'failed', preventDefault() {} } as ErrorEvent);
+    if (reason === 'messageerror') worker.onmessageerror?.();
+    if (reason === 'invalid') worker.onmessage?.({ data: { ok: true, data: 'bad' } } as MessageEvent);
+    await rejected;
+    expect(worker.terminate).toHaveBeenCalledOnce();
+    expect(vi.getTimerCount()).toBe(0);
+  },
+);
+it('rejects an already canceled request without constructing a worker', async () => {
+  const worker = vi.fn();
+  vi.stubGlobal('Worker', worker);
+  const controller = new AbortController();
+  controller.abort();
+  await expect(runSpreadsheetWorker('csv-to-xlsx', 'a', controller.signal)).rejects.toMatchObject({
+    name: 'AbortError',
+  });
+  expect(worker).not.toHaveBeenCalled();
+});
diff --git a/test/unit/sw-boot-precache.test.ts b/test/unit/sw-boot-precache.test.ts
index add410f87..38a814162 100644
--- a/test/unit/sw-boot-precache.test.ts
+++ b/test/unit/sw-boot-precache.test.ts
@@ -81,13 +81,16 @@ it('caches vendor bootstrap script and style tags without evaluating inline scri
 
 it('installs native export runtime before the editor is used offline', async () => {
   const listeners = new Map<string, (event: any) => void>();
-  const stored = new Set<string>();
-  const cache = {
+  // Per cache name: the network-first offline fallback only reads the core cache.
+  const stored = new Map<string, Set<string>>();
+  const cacheFor = (name: string) => ({
     addAll: async (urls: string[]) => {
-      for (const url of urls) stored.add(url);
+      const entries = stored.get(name) ?? new Set<string>();
+      for (const url of urls) entries.add(new URL(url, 'https://editor.example/').pathname);
+      stored.set(name, entries);
     },
     match: async () => ({ text: async () => '<html></html>' }),
-  };
+  });
   runInNewContext(readFileSync('public/sw.js', 'utf8'), {
     URL,
     Promise,
@@ -98,7 +101,7 @@ it('installs native export runtime before the editor is used offline', async ()
       addEventListener: (name: string, callback: (event: any) => void) => listeners.set(name, callback),
       skipWaiting: () => {},
     },
-    caches: { open: async () => cache, keys: async () => [] },
+    caches: { open: async (name: string) => cacheFor(name), keys: async () => [] },
   });
   let installed!: Promise<unknown>;
   listeners.get('install')!({
@@ -107,9 +110,17 @@ it('installs native export runtime before the editor is used offline', async ()
     },
   });
   await installed;
-  expect(stored.has('/sdkjs/common/wasm/x2t/x2t.js')).toBe(true);
-  expect(stored.has('/sdkjs/common/wasm/x2t/x2t.wasm.br')).toBe(true);
-  expect(stored.has('/sdkjs/common/wasm/x2t/x2t.worker.js')).toBe(true);
+  const cached = (prefix: string) =>
+    new Set([...stored].filter(([name]) => name.startsWith(prefix)).flatMap(([, urls]) => [...urls]));
+  const runtime = cached('document-editor-runtime-');
+  const core = cached('document-editor-core-');
+  expect(runtime.has('/sdkjs/common/wasm/x2t/x2t.js')).toBe(true);
+  expect(runtime.has('/sdkjs/common/wasm/x2t/x2t.wasm.br')).toBe(true);
+  expect(runtime.has('/sdkjs/common/wasm/x2t/x2t.worker.js')).toBe(true);
+  // Not vendor assets: activation prunes them from the runtime cache, so their
+  // offline copies belong to this build's core.
+  expect(core.has('/libs/sheetjs/convert.worker.js')).toBe(true);
+  expect(core.has('/libs/sheetjs/xlsx.full.min.js')).toBe(true);
 });
 
 it('precaches local file-open controls from the offline homepage', async () => {
diff --git a/test/unit/sw-routing.test.ts b/test/unit/sw-routing.test.ts
index 0df7c361d..382468c31 100644
--- a/test/unit/sw-routing.test.ts
+++ b/test/unit/sw-routing.test.ts
@@ -19,7 +19,7 @@ const FONT_REGEX = /\.(ttf|woff2?|otf|eot)(\?.*)?$/;
 
 /** Keep in sync with DEPLOY_COUPLED in public/sw.js and the no-cache group in public/_headers. */
 const DEPLOY_COUPLED =
-  /^\/(?:home|landing|app-tokens)\.css$|^\/(?:lang-switch|sw-register|open-local|landing-prefetch|history-recent|theme-presentation)\.js$|^\/ranui-iife\//;
+  /^\/(?:home|landing|app-tokens)\.css$|^\/(?:lang-switch|sw-register|open-local|landing-prefetch|history-recent|theme-presentation)\.js$|^\/ranui-iife\/|^\/libs\/sheetjs\/convert\.worker\.js$/;
 
 const isHtmlRequest = (mode: string, pathname: string): boolean =>
   mode === 'navigate' || pathname.endsWith('.html') || pathname === '/' || pathname.endsWith('/');
@@ -187,6 +187,9 @@ describe('deploy-coupled assets use network-first', () => {
       '/history-recent.js',
       '/ranui-iife/button.iife.js',
       '/ranui-iife/card.iife.js',
+      // The SheetJS worker's message protocol changes with the app bundle that
+      // posts to it; a stale copy fails the first conversion after a deploy.
+      '/libs/sheetjs/convert.worker.js',
     ]) {
       expect(strategyFor(path)).toBe('network-first');
     }
diff --git a/test/unit/workflow-contract.test.ts b/test/unit/workflow-contract.test.ts
index 1de44abc3..e6bd59b52 100644
--- a/test/unit/workflow-contract.test.ts
+++ b/test/unit/workflow-contract.test.ts
@@ -1,5 +1,5 @@
 import { readdirSync, readFileSync } from 'node:fs';
-import { resolve } from 'node:path';
+import { matchesGlob, resolve } from 'node:path';
 import { spawnSync } from 'node:child_process';
 import { createRequire } from 'node:module';
 import { describe, expect, it } from 'vitest';
@@ -543,6 +543,12 @@ describe('.github/workflows/nightly-corpus.yml', () => {
     for (const vendored of ['public/sdkjs/**', 'public/web-apps/**', 'public/fonts/**']) {
       expect(oxlint.ignorePatterns, vendored).toContain(vendored);
     }
+    // Our own scripts can sit next to a vendored bundle (the SheetJS worker beside
+    // xlsx.full.min.js); a directory-wide ignore there silently drops them.
+    for (const own of ['public/sw.js', 'public/libs/sheetjs/convert.worker.js']) {
+      const ignoredBy = oxlint.ignorePatterns.filter((pattern) => matchesGlob(own, pattern));
+      expect(ignoredBy, own).toEqual([]);
+    }
   });
 
   it('drops the corpus fuzzer output without dropping real bug-report files', () => {